If you have in-floor heat, and you are afraid to screw down the adapters, you could caulk them down, barely tighten the back bolts, and rely on caulking to stick the bowl to the floor.
PolySeamSeal will stick it, Silicone would be almost impossible to pull back up.
Anything with Sanagloss would be good. The Drake II, CST454CEFG or Ultramax II MS604114CEFG
These don't require the adapters.