I run mine at 20 lbs.

It's really a personal preferance.  I not only tow my GN horse trailer. But almost daily have a Skidloader or mini excavator hooked up to the bumper hitch.

All depends on the bags, trailer and what kind of ride you are looking for.

My truck has a CM Hauler bed with Firestone bags and we pull a Sundowner 3 horse trailer with a 10LQ and I run my bags around 70psi all the time.  This figure with differ from truck to truck.  It took me a hand full of times changing the psi to find what works best for me.  Too little does no good, too much makes a stiffer ride but hold the trailer up good.

Hope this helps, HTB

I would start with around 80 psi and see what happens, this should be too much, but it is faster to let air out than put air in.  Drive it a few miles loaded then let around 10psi out then try again.

The pressure is really going to be a personal thing. No two drivers are going to use the same.

Heck I watch the guy who bought my LQ, back under it using his onboard camera.  He had let all the air out of his airbags. When he got under the hitch, he turned on his on board comrpessor and infated his bags to max pressure. Which lifted the ball up into the hitch. He got out and put up the jack and hooked up the chains and drove off. I think he choice of pressure was what ever it took to lift the trailer off the jack.