laying marble tile in bath?

Have a 1995 Damon Intruder. Just got back from Wintering in Fl. The bath, smallish as it is, has been quite usable. However, the carpet has become stained and worn, so we decided to put down marble tile. I discovered they laid the carpet, then put the walls, cabinetry, shower and toilet directly on top of the carpet...never heard of that one!. The subfloor is chipboard. A 'search' suggested putting Hardy Board on top of the chipboard. No way I'm going to try to fit that stuff in such a tiny space! So, the question becomes: what kind of adhesive to put the tile in with. As of now, I'm considering panel adhesive...non-water based. Most tile adhesives are 'water cleanup', which I'm afraid will add to the possibility of buckling, though I must say the chipboard has not buckled next to the shower where it has obviously spilled. Supposedly, there adhesives specially for chipboard, so need a trip to Lowe's. Any thoughts on this? Bill