The goal of this build is to achieve the highest thrust to weight ratio for insane acceleration and speed.

Overall this build is ultralight at AUW of 410g (including batteries) and can develop more than 6 Kg of thrust thanks to powerfull 2306 motor powered by 6s for really insane ratio of more than 15 to 1! It's also very compact (195mm motor to motor) and aerodynamics.

Here I will explain why I choosen each components:

1) Frame: DRC Fury 5X Lite. t's the lightest 5 inch frame (only 50g) that can offer decent durability and protections to all the internal components (camera, etc...). I like very much the quality of this frame and I think it's also cool as appereance. The design is a true-X that is quite all rounded and can fit both racing and freestyle (even if this build is pretty much oriented to racing). It's very very compact and not even 1 mm is wasted. I think it's close to impossible to make a 5 inch more compact.

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2) Motor: Emax RSII 2306 1700kv. Very lightweighted (26g w/o wires) and powerfull (developed almost 1.9 kg of thrust on the bench) while still efficient. No other motor can develop so much power at this weight. F40 PRO II would also be a great choise, and perhaps even more safe (RSII are still to be proven relaiable), but at the end I opted for RSII 2306 because they weight 1g less and I'm also very curious to try this new creature of Emax.
You could get marginally more power from bigger motor (like F60 or other 2207) but at the expense of more weight and also more amps draw, that would force you to put a bigger LiPO that would dramatically increase total AUW (a 1300mah liPO would cost 60 more grams...).

Tips for build: I replaced the standard screws of the motor with aluminioum ones (you can find link in the spare part); this can save you about 10g that is pretty much, and 4 aluminium screws are still enought durable and much better than 2 or 3 steel ones. The best would be to use 7mm screw (that are hard to find), so either you use 6mm (less durable) or you get 8mm and cut down to 7mm.

3) Prop: Emax AVAN Flow 5 inch. This props are designed specifically for RSII 2306, so should be a perfect fit. This props provide also very good grip in the air, while being not too much heavy for battery (much better than AVAN R that were too much amps hungry).

4) ESC: Hobbywing XRotor micro 45a 4-in-1. As I said Fury 5 Lite frame is very compact and not all 4-in-1 esc will feet inside (like the Aikon is too wide). The Xrotor micro is perfect for this frame and fit perfectly inside (see picture below), while having all the spec that you can ask from a ESC: Dshot 1200, BlHeli 32, 6s compatible, soft mount, etc... Also they are capable of 45A (at least in theory... XD) that should be enought to handle this kind of motors (RSII 2306 on 6S)

Tips for build: This XRotor esc comes with 2 capacitors (470 and 1000). Be sure to USE the big one, especially with 6S. This esc work quite well with the capacitor and there isn't much noise. But if you try to use it without capacitor it's pretty much a mess and many people had this esc blew up.

Tips for build: If you want to save even more weight you can solder the XT60 connector directly to the esc and avoid the pigtail that is quite heavy. I didn't made this and even if I kept the cable as short as possible, it costed me at least 10g of extra weight, probably I could get under 400g AUW without this (even if it's quite riscky to solder the connector directly to the esc, in case your battery get ejected could brake your esc but... no pain no gain...).

5) Flight Controller: Helio Spring. I think that this FC is very innovative, it uses 2 chip: F4 as the main + a F3 dedicated to filter and clean the giro. With this solution you can run full speed (32khz) and getting a very clean signal from the giro. The results is exceptional flight performance, with the quad that seems really locked in the air and the prop wash a far far memory.

This Helio Spring is compatible with XRotor esc and you can plug directly them together without any problems.

Of course this FC works only with butterflight, so if you don't like it you should change FC.

Be sure to buy Helio Spring V2, since the V1 can have problems when mounted too much near to the 4-in-1 esc, like in this build. If you still have problems even with the V2 I suggest to cover the ESC with a copper layer to prevent noise.

Tips for build: When you build your stack on this frame you should keep in mind 2 major points of attention:
(A) the standoff are only 16mm so your stack should be very very tight.
(B) The screw used on the stack will works also as one of the 2 anchor points of the arm to the center and bottom plate. So I strongly suggest not to use the 5mm nylon standoff provided by DRC to mount the base of the stack.

To solve both (A) and (B) I got 4x22mm aluminium screw, 4xaluminium nuts and 4xrubber o-ring and I mounted them as you can see in the 2 picture below (note: in the first picture I managed to get red aluminium nuts to better fit color of the build.... XD). You cand find in the spare part the links to the material I used.

I find that this solutions is very good because provide at the same time: enought solidity to keep firmly the arm locked to the plates; allows to get the stack very tight and both the FC and ESC are softmounted.

6) Camera: Predator Micro v3. It's a great racing camera providing very low latency and lightweight. Also a runcam sparrow or racer could be a good choise but with v3 I think that foxeer got a very good edge on runcam since they removed the blue cast (that was the major problem of the predator), they double fps wich I find is great (50 PAL, 60 NTSC) and as icing on the cake it's 16:9/4:3 and PAL/NTSC switchable.

Note: I used Predator Micro v2 since I already had this camera, but I plan to upgrade asap to v3. It's a great leap forward in my opinion.

7) VTX: Runcam TX200U. It's not the best VTX on the market, but it's the incredible light (only 2.5g with antenna included!) and good enought if you don't plan to do mid/long range. And it's also not too much expensive.

Tips for build: If you mount this VTX on the back of the camera like I did, you will be quite struck with the connector of the esc and you will not be able to angle the camera less than 40-45° minimum. See the below picture where you can notice that VTX is already pressed between camera dn esc connectr and don't allow to lower the angle of the camera.

8) Receiver: FrSky R-XSR. Tiny, light weight, with smartport telemetry and diversity. Can you ask more?

Tips for build: At the end I decided to mount it directly on the top plate and place the antennas on the top also. In this case they are less protected in case of crash but it will be much easier to open the build for repairing and should provide also a better range.

Tips for build: I suggest to flash the F-Port firmware, get rid of the green cable (SBUS) and connect the yellow cable (S_port) directly on the SBUS pad of the helio spring (see below picture). In this way you will free 1 UART, get a better protocol (F-Port should be faster) and, most important, you will not be forced to disconnect the FrSky to be able to put Helio Spring in bootloader mode directly from Butterflight.

9) Battery: Tattu R-Line 1050mah 6s. 1050mah are much lighter than 1300mah (170g vs 236g, almost 70g of saving!!!) while the great quality of Tattu R-Line with high-C and low internal resistance allow you to provide enough power to the RSII 2306 motor even with 1050mah.If you want now there is also the HV version for a little extra...

You can also choose other LiPO but I suggest to get something in range of 1050-1100mah and high-C for weightsaving without getting too much voltage sags and compromising the performance. However in any test that I seen the Tattu are line are simply the best.

And here you can see the final build, that weight just 410g battery included :-))))

As soon as I can I will try to post some flight footage, but don't blame me... I'm still a terrible pilot...