Appropriate overlap of wall around tub

Jerrys84

Hello,

I am looking to put up backerboard around the tub to tile on. I had to shim the studs out a bit to get to the tub, but now I am looking at the porject and wondering if i really needed to shim them out as far as I did.

Right now, the shims just (1/16) overlap the edge of the tub. I realized that including the 1/2 inch cement board and then tile and what not. I may be way overshooting how much of an overlap the wall should have with the tub. What is the minimum amount of overlap necessary? I am wondering if I should take out the shims and use thinner ones.

Thanks for any advice!