Since I've left mine pumped up to 60 psi, I've noticed more rattling of stuff in the back (like my toolbox). I'm leaving them pumped up because I have more trailer towing to do shortly. But you can just drop back down to 45 psi and it's not noticeable to me...
It could be difficult to find LT -rated tires for 22" wheels that aren't substantially larger (in circumference) than your P-rated tires. I have the factory 22" wheels and have yet to find anyone that makes an equal size LT for it (284/45R22). But I DID find that Cooper makes the Discoverer AT3-4S in a well-rated trim (better than factory) ...and I believe they are 10-ply tires. I've run Coopers on all my vehicles for 20 years now and have always been impressed with the improved and more stable ride quality.
Before I layout the cabbage for new wheels (to be able to get LTs) ...and new tires, I'm probably going to try a set of these "regular" Discoverers. Of course all bets are off if I decide to lift the Expy. Then 18" wheels and 33-35" tires (LTs) for sure.