While not a solution to anyone's specific issues when having too little clearance, the overall issue is the truck industry and RV industry not working in concert. When trucks, specially Ford, continue to raise bed and bedrail heights that's one side of the problem. The other side is RV companies trying to keep overall bed ceiling height below the 13' 6", and keep good headroom in the overhang bedroom, they don't raise the bottom height of bedroom to allow for level hauling with bigger and bigger trucks. A miss match that creates all these problems.
I didn't see any comments about ensuring that the trailer is running level and not uphill placing undo stress on trailer rear axle. I know some folks rely on putting rear axles under leaf springs to raise the trailer, but may or may not work on any specific trailer.
My 2017 Chevy 3500 SRW fortunately matched up pretty good on my 2015 Keystone High Country, running pretty level, 6" clearance and total height around 12' 8" to top of air conditioner. I'd love to see the truck and RV industry come up with some standards that would make these issues go away.
2017 Silverado 4WD crewcab SRW longbed diesel
2015 Montana High Country 293 RK