Longevity of floated concrete slab on RW3

Hi Guys Just a quick one here before I start getting into a new build. I'm looking to float different slabs for the individual rooms in a new set up and rather than use proprietary spring systems I'm leaning towards floating them on RW3 (much more cost effective). Each room is to be constructed of blockwork walls, concrete floor and concrete lid My first concern is that, having read through countless posts on this, the suggested method is to have: one layer of RW3, a layer of plywood, a second layer of RW3 a polythene sheet poured concrete slab Given the variable of room sizes and therefore weight - how can i be sure that this structure won't compress too much/too little under the weight of the new room? Secondly, using this RW3/Ply sandwich - wouldn't that cause a loss in STC? I've also read a new sticky (new since last time I was here) that negates the positve factor in using floated floors. Given that we have already cut the existing slab (to a depth of 12" or so) and it rests on a chalk base - do you think these additional slabs would be overkill or worth doing. I am going for maximum isolation on this one guys! Would really appreciate some input :)

generally you don't sandwich the floor that way. usually you layer (top down) - concrete - sealing membrane - plywood or other evening layer - RW (or commercial isolators) - base materials