I thought I'd show you the nearly final result -- I couldn't be happier with the positioning for both shower users (the position is out of the spray so the soap doesn't get wet) and the tub users (you can reach the soap and the shampoo while still soaking in the tub. I have 8' ceilings, and measured so the base of the niche was 57" from the ceiling and the near side of the niche was approximately 8" from the near wall (worked out well for me with the existing studs)
Q
NICHE location: with 8' ceilings, and measured so the base of the niche was 57" from the ceiling and the near side of the niche was approximately 8"
Q