A little background.  Have gone through 3 mattresses over the last 3 years trying to find one I can sleep comfortably on. I started with a memory foam that eventually killed my lower back.  Moved on to a sleep number which when set very firm, solved the lower back issue but I tossed and turned all night with the pain felt in the areas I was laying on(pressure points).  My last attempt was an adjustable bed, a split Cali King.  It came with a memory foam mattress that I suspected wouldn't work.  It didn't, as I sink way down. I know I need a firmer mattress and want to construct one out of foam.  It needs to be 8 inches High.  I was looking at Foamorder.com. They have a very firm conventional foam called V90 I would use as a base.  I called them and they suggested 3 inches of the V90(ild90), 3 inches of the V54(ild45) and 2 inches of some kind of comfort topper- possibly latex.  I am looking for feedback as I am getting really tired of spending lots of cash on beds.  I am 6'6, 290 lbs and sleep on my back or on my side.  Help!