polartuner -
Use to own a tile & marble company, so have a few ideas on this.
First, if you where a customer of mine I would say don't use it. As the chassis tweaks it is going to cause problems with the tile cracking at some point. We had a customer who had custom tile in 3 bathrooms ($85 per 4"x4" tile) in a 65' Sea Ray with (2)12V twin turbo cats hooked to KAAMA drives. We replaced tile everytime the water was 4 plus footers, because he could not lay off the throttles.
But if you have to have it here are some things you can do to hopefully limit the potential for problems.
Not sure of your under layment, but if you can fit it in (not sure of the surrounding materials and their heights) include metal lathe stapled then fill with planicrete witch is a highly flexible self leveling product. I would even consider modifying it with a acrylic additive, which will give it more flexibility. I would use this instead of a sheet of luan or thin plywood if you have to build up to meet up with carpet or wood.
Use a good glue to adhere the tile, this is good and flexible. And then use a good quality grout (mapai or equal) and use solid acrylic additive instead of water. This will give the grout alot of flexibility and less chance for it to crack or chunk out.
Just some ideas.
Bill
2003 28' Show Hauler Motorhome on a 1995 FLD 120
www.showhauler.com