[Bob Mariani]

No vapor barrier behind the wall. If using a solid surface wall there is nothing to protect from a wet condition so even the durock is not needed. The wall material should lap over the lip of the shower base and be caulked. The solid surface is left 1/8" above the base and caulked again.

 

[Bob Mariani]

I would leave the light centered in the shower. Otherwise you only get a shadow of light.