I fail to see the issue with airing down. A 35" tire on an 18" rim has the same sidewall as a 33" tire on a 16" rim. A 35" tire on a 20" rim has the same sidewall as a 31" tire on a 16" rim. Those smaller sizes air down just fine as do my 35" toyo a/t on my factory Ram 20's. These aren't low profile tires. Far from it. And modern diesel trucks run 35" tall tires without sweating a bit. A Ford Super Duty with 20" wheels comes stock with 35s in a 275/65r20. My 2014 Ram 3500 srw runs like a dragster with 295/65r20 Toyo A/Ts, even with my Lance 855 loaded and it is only available with 3.42 gearing. Oh, and they are rated for 4080# each.
These "rules" may have applied a decade ago when every truck came with 16" wheels and less powerful motors and tires were all rated at 3750# max. Current model trucks are more than capable of running 35" tires stock with power to spare and those 35" tires are more than capable of airing down and carrying serious loads safely. I've done Stoney pass in Colorado (a 5 rated trail) in an F150 with a popup truck camper loaded down with a stock height suspension and 275/65r20s. It was more than capable of that and Engineer as well.
