This is probably useful information for this thread:
I use the Ikea "MINNESUND" mattress. Size "full." It's designed for a slatted base. The cover is removable and washable. I cut the foam to width, folding the excess cover in equal parts under each side. Length-wise it's a few inches short, but not noticeable.
Fitted with two sheets, the shell closes onto it, and may even compress it a bit -- so, I would say that 3 7/8" is the maximum mattress thickness compatible with a Campteq.
MINNESUND Foam mattress - Twin - IKEA
Im slat bed and a ~3" EXPED with full beding and an insulated top