Out of further curiosity, which bits did you have to file down? I picked one, and it definitely does not seat and lock properly on my Elite either.
It locks just fine disassembled, so its definitely the little spring loaded plastic bit opposite the ball that is impeding it. I'm just not sure which part of the piece is stopping from moving forward enough to seat, the bit that the front of the trigger guard hits, or the bit at the back that locks inside the guard.