Wife has chosen 610mm x 405mm classic travertine tiles but I'm a bit apprehensive about laying such large tiles, I had originally suggested 457x305. I have dot and dabbed on new moisture board and it's almost perfectly flat, I've also tanked the shower and bath areas with homelux membrane so I reckon the walls will be ok. I plan to level up the wooden floor as much as possible and add extra noggins for strength before the final fitting of 25mm marine ply. I know I need flexible powered adhesive and grout but not sure which colours or brands would be best. Is 10mm the best size trowel to use and are there any other pitfalls to look out for.