I'm in the process of remodeling my bathroom and am about to start tiling in the next few days, I noticed that the cement board has a small valley about 1/8 of an inch on a 3x5 durock cement board where the shower head and faucet are. Can I level out the cement board with modified thinset to have a flat surface to lay the tiles on? I drew a super quick illustration:
I suppose it's a bit comical but I hope it's clear what I'm trying to achieve, it's not drawn to scale. I guess my fear is that the modified thinset doesn't bond well to the cement board and the tile weakens and eventually falls. I appreciate any advice.