This may be as interesting as watching the grass grow, however I need to let Jayco owners know there is an answer to the cracks in the shower floor.
As reported before we were getting large cracks in the floor. Jayco had no answer so I bit the bullet and put down some fiberglass patches.
All well and good for a time, however the bits outside the patches started cracking. BUGGA!!!!
I went to a Murray Bridge composites mob, after explaining the situation I picked up some 400GSM mat (fiberglass) resin, and a can of white flow coat (as suggested on this forum)
Long story short. I put a full cover of glass down, 2 coats of flow coat and bingo works like a charm.