I've had two vehicles now where I've changed from 'ten-ply' truck tyres to LT tyres. The first, a Daihatsu Delta van, anybody would swear had had a complete suspension replacement. The difference made was enormous, went from bone-jarring to fine, with just a wheel and tyre change. The OKA wasn't so dramatic because the suspension was already very kind. But that's what squishy sidewalls are doing for your camper trailer too - getting rid of the jarring - some of what shakes your kitchen to bits and smashes the eggs in your fridge.
The BFGs may well have a '10-ply' load rating (maybe not really in Isuzu size), but they almost certainly have three-ply sidewalls (a couple of sizes have four-ply). They're much kinder to your contents and assembly than the six-ply or eight-ply sidewalls that 'truck' tyres have, and that's what the manufacturers are wanting to keep you away from (and rightly so). Tyre pressure is not a cure-all; any tyre with a six-ply sidewall will be a lot harder riding than a three-ply sidewall at the same pressure.
What you should be looking at is the load rating - if you have a trailer that never weighs more than 1000kg and you have a pair of tyres capable of carrying three times that, they're going to be hard-riding and your rivets will shake loose and your limiting straps will get a workout if the pressure's up. BFGs are probably as good as any other LT tyre in this regard, and the load rating is probably going to be given at 65psi and may be frighteningly high; but fortunately with three-ply sidewalls, keeping the pressure down to something less than half that may be entirely appropriate.
