Honestly it sounds like the feigao motor's hole's are stripped or starting to strip. I say this as because I just drilled & tapped new holes in my feigao 7XL the holes are 3mm x .5 thread. So ya your titan motor screws should fit, I suggest going out and buying a cheap drill & tap metric set they come in handy big time with rc stuff, not just for aluminum they work on plastic too.