Mattress Forum

One concerns foundations. I've learned here about Euro slats. It seems like a flexible option for me, comfort wise, and I can add legs now and put it on a frame or platform later if I choose to. Flobeds sells one and I'm leaning toward that. I've read on this forum that a thinner mattress is preferred for use with these. But how thin, does anyone know? 

My second question, I see that some companies offer a 6" thick latex in addition to or instead of multiple 3" layers. Beyond the doubling in weight for one piece and the flexibilty to custom make the bed (ease of shipping, moveability, etc...), what is the difference between, say,  one 6" firm and two 3" firms?