Just where the tub was is fine----
I do suggest that you water proof the new board with a paint on waterproofing like Red Guard or a surface membrane like Kerdi----
Any thing above the shower head will never get wet enough to worry about---
I do suggest that you water proof the new board with a paint on waterproofing like Red Guard or a surface membrane like Kerdi----
Any thing above the shower head will never get wet enough to worry about---