[travelin texans]

If you've got original G rated tires then that says that rig is or will be very heavy so my opinion is leave them at 110 psi or whatever the sidewall recommends for max weight. If you lower the pressure you'll probably have irregular tire wear due under inflation or have high temperatures that could cause blowouts.
As George pointed out your truck Is a little lightweight for that rv loaded which is likely the cause of your bumpy ride & not tire pressures. So air up the truck tires to their max load pressures also to help haul it.