I have thick paver style tile over concriet, started to bust up tile to get to slab and lay new tile. When busting up old tile it is severely damaging slab with deep pits. The old tile is stuck very well, I want to lay new tile over the old pavers. I have sanded the glaze off and am happy with that, the problem I have is that the existing pavers have some pretty severe cupping at corners. Question is do I do a scratch coat the spead the floor with a notched and then butter the back of the tile to get me over the cupping. Any help, suggestions, or advice would be appreciated. I have lots of experience laying tile floors, showers and counters I just have never layed tile over tile and the cupping issue is concerning