This is one of my earlier ultralight 2.5" builds which at 53 grams dry floated like no other 2.5" micro I've ever seen.
The sacrifice for that float was smaller motors/less horsepower, these old school Racerstar 1103 8,000's are only 3.3 gram each by sacrificing the screw holes since you really don't need them at this power level. Because of this I used a Kyocera 1.47mm drill bit to run through props when replacing them to make sure the hole isn't too tight which could push the motor shaft down out of the bottom of the bell. If the prop is too loose on the shaft, all you needed to do is put a tiny bit of superglue on the tip of a pin/clothes pin/paperclip, smear it around inside the hole of the prop, let it dry, and then run the drill bit through it by hand again to make sure it's not too tight. The residue of the dried superglue is rough and allows the prop to bite against the motor shaft.
The FC has blackbox which really helps with tuning, but as you can see from the video I have it locked in and ready to go.

The batteries I ran on this rig were...
15.2 gram 2s 300mAh
17.5 gram Nanotech 2s 300mAh
20 gram Sky Hobbie 2s 350mAh
22.2 gram Mad Dog 2s 350mAh

uSmile 100mm Carbon frame
Omnibus F4 FC w/blackbox
FrSky Xm Receiver
Babyhawk 200mW camera
Old school Racerstar 3.3 gram 1103 8,000kv motors
Racerstar 6A 4in1 ESC