All I can share is that my spouse did not complain about sleeping on a hard board...he said he felt like he actually slept.
I think the Anti fatigue mat in a tent trailer will also add insulation under your bed boards - might prove to serve a double duty!
Hope you find relief the way my husband did! Harbor Freight sells a 4 pack of 25 x 25 squares for 10-, it took 6 squares for our bed area.
2012 FR Flagstaff T12SDTH
1996 Shadowcruiser Pop Up Truck Camper
1967 Newell Motorcoach
2003 Ford F150 5.4 V8 Triton Super Cab
2004 Nissan Titan LE 5.6 V8 4x4 Crew Cab