Just bought some 3" memory foam. And just barely got the king side closed up. Had to extend my latches almost all the way to the end of threads. we had 1 1/2" on that end and on the queen end we had 3" foam on it. I think with extra canvas that the king end has it made it tougher to compress down. Go back out tomorrow and see if i can recover some of my latch threads after all the air is out. The 3" foam seems like it will make a big difference for me and the Wife's old bones.