Update 23/5/20: Changed the brittle stock canopy to a 3D printed TPU canopy for the Eachine F7 AIO Camera. Adds about 0.5g and a lot more durable and also mitigates the camera being pushed back into the canopy during crashes. I also tied down the battery lead to the frame with dental floss to prevent the power leads from being ripped off from the CBF3 during a crash.

With the advent of super-powered 1S brushless whoops in late 2019 such as the Meteor65 and Mobula6, I set out to find if my old Eachine US/UK65 could stay relevant amid the crowd of new technology, thus I set out to mod it to be faster, more powerful, and lighter.

Dry weight of my quad and the contenders:
Mobula6: 19.76g (according to Gal Kremer)
Super Eachine UK65: 22.5g (according to my crappy weighing scale)
BetaFPV Meteor65: 22.8g (according to Nick Burns)
So, my quad is not the lightest but it is definitely still quite light, as it stays below the 24g dry weight needed for good performance.

BetaFPV Beta65 Pro Frame
Better than the original brittle frame, not expensive, and around the same weight. Highly recommend changing ASAP as the stock frame is really bad.

Happymodel 0802 19000kv Motors
A significant upgrade over the stock 0603, which are the same KV but ridiculously less efficient. Average amp draw on 0603 is 5.5A but only 4.3A on the 0802, leading to 45 seconds more flight time. The top end power is the same as the KV is the same but there is more low end torque on the 0802, similar to how a 2306 motor has better low-end control than a 2207 due to the wider stator. This is the most significant upgrade to the UK65.

Solid-pin PH2.0
This upgrade is a must-have as the voltage sag on the stock crimped pins with U-shaped hollow connectors is terrible, sagging to 2.8V at the end of the flight, while solid pin allows voltage to stay robust at 3.1V and above throughout the flight and is better for battery life. I cannot stress how important this simple upgrade is for longer flight times, more power, less overheating, lower amp draw and better health of the 1S batteries.

Gemfan 1219
These props are incredibly hardy, I have flown the same pair for a few months and not a single one has broken after numerous crashes. They also have good efficiency and control and I cannot tell the difference between it and a 4 bladed prop while turning tight corners. The only downside is that it is near impossible to turtle mode. I also tried Gemfan 1224, Eachine E010 stock props, BetaFPV blue props etc but none were as good as the Gemfan 1219.

Betaflight 4.1.1 Performance Edition
It is now possible to get Betaflight 4.1.1 with all its amazing functionalities on Brushless F3 boards like these. I flashed 4.1.1 with target CRAZYBEEF3FR .hex file and it flies well!

Conclusion: US/UK65 can still be relevant in 2020 :)