My 4″ foam block is also deforming.
But that’s O.K. since I now think 2.5-3″ of lift would be enough.
Why? The truck frame is a lot more stiff than earlier Fords.
The rooftop antennas are at the rear, so any porpoising clearance would affect the front of the cab more and the rear less.
What you can do is buy a 4×8 sheet of 1/2 inch outdoor plywood; cut in half the long way and spread it out against the wheel wells with an MT slot down the center and use leftover pieces cut to be spacers/keys in the slots. Maybe finally add an extra thin rubber mat and lower the camper on.
All this fiddling is on going.
There are lots of variables, not the least of which is how much off road the operator does.
2020 Ford F-350 XLT FX4 4WD SRW SB SC 7.3L Godzilla Gas TorqShift 10R140 397 amps dual Alt dual batts Frnt Dana 60; Rr Dana M275 E-locker 4.30's 4580/4320/4066# payload 7243# curb wt. 11,300# GVWR 5-er prepped. 2020 Northstar Laredo SC, 12v compressor fridge, cassette, 320w Solar sub zero insulation.