I'm planning a diy foam mattress, hoping to use as little topper material as I can. I was thinking that FBM's HD36-HQ would work well for what I need, in terms of density and firmness, but I read a post from LatencyMachine from 10/12 that has me concerned that the HD36 might soften too much over the course of several months. For those of you who've used FBM's HD36, have you noticed a similar softening? I'm leaning toward just getting the too-firm Lux-HQ and toppers since it seems like a safer bet, but if the HD36 doesn't soften too much, I could get away with not having to buy as much topper material.

Thanks,
Jim