Nah, I got what you meant

Yep, too much downthrust will cause pulling to the belly in a stalled condition such as KE, hovering, etc...Also you may have a bot of up trim in the elevator to compensate

I had the same Kangke Cap and did not notice what your father is seeing, that's a weird change

The prop change was jsut an after thought. I did not think about the current setup and what it probably took to get it to balance