MorganS:
The CH340G controls the Rx pin no matter what you put in your program. I think your only choice is to desolder the LEDs. Hacking into that chip's power supply is more likely to brick your board.
Okay, that is a bit unfortunate but makes sense.
Wawa:
I assume two Lipo cells in series (7.2volt).
Anything less than 6volt on V-in could do unexpected things.
Leo..
Yes, that is exactly what I am doing. Sorry for not specifying.