I just re-read your original post, I think I may have thought you were talking about the bench seat, I realize now you were talking about the pop top bed, right?
Anyway, when we swapped over to a CCV poptop we opted to upgrade the pads with natural latex, we found even then, 3” wasn’t enough and I ended up adding a 2” memory foam to it (for a total of 5” for you mathematically challenged) and had the covers redone. Was torn on adding the memory foam, especially to the natural latex, as I genuinely hate the stuff but it works to add much needed pressure point relief.
'03 Ford E350 7.3L Diesel
(de)SMB'd Custom RB-50
Quigley 4X4 w/Deavers & Agile Offroad's R.I.P. package
CCV High Profile Pop Top