I replaced my shell and now sync doesn't work.

I bought some new skins for my Xbox 360 controllers to make them look cool and i had a lot of trouble getting the sync button in when i push in the PCB the sync button wont lign up right. I read that i could shave the bottom of the button and it would work. any other ideas before i alter it so i don't mess it up? also any ideas on how to shave it in case there isn't a better idea. should i use sand paper or an Xacto knife?