I'm having trouble understanding what you mean by this step:
"Since the plastic on the inner corners of the D-pad is so thick, there'll be no room to press anything unless you remove some of it. You'll want to halve the thickness of the plastic on the D-pad's inner corners, removing the top half."
And the picture you supplied to illustrate this is pretty blurry, so I'm having a hard time making out really what you're describing.
Is there any way you think you can re-state your intentions?