Since I have a sum total of one tire mounting experience under my belt, I'm not going to suggest anything, but I'm curious....The bias ply tire 16-20 NDCC tire for my 8x8 has a date code of 499, (which probably is 1989) and is far stiffer than described above. After almost twenty years, the bead to bead measurement was 14 inches and laying the tire down, I could stand on the beads with very little deflection.
After I managed to get the tire on the wheel and the ring installed, it was air tight and I could take my time filling it with air with small pops now and then as it adjusted itself. A couple of final large pops seated the tire against the rims when the pressure reached 35 psi.
The truck TM calls for 10 psi in mud and snow and I'm wondering if this sidewall stiffness and tightness on the wheel, which also has the "safety humps" are all part of the requirement or is this normal for bias ply tire? The tire is rated "10 ply".
If everything goes according to plan, I'll have a chance to mount one of the Goodyear MVT radials next week. It'll be an interesting comparison.