Help me get the right rims.

Im a bit confused on how to select the right size rims.
Basically I would like to get a set of 15x8 rims. I plan on running 33x12.5 15 tires.
So if the stock BS is 4.5" and the rims I have my eyes on are 4" BS with 1/2"
of neg offset. Will that pretty much bring the center line to the proper position? Although with running a wider tire and rim, do I need to be thinking about diff BS and offset? If its possible to get the center line in the proper area running wider tires and rims, im worried about bearing wear and handling.
Hope that makes sense, thank you.

 

I think you will want less than 4" of backspacing to run 12.5's.