The answer to "What pressure do *I* consider safe" might well kill you..
The correct question is: What pressure is PROPER for your RV.
RV Safety & Education Foundation
Go there and follow the links to the one for weighing your rig, it is a reasonable fee.
The procedure starts with a telephone or E-Mail "Interview" (What tires do you have and things like that, Where is the rig parked) Then they come out and look for a flat spot to scale you.. Then they use calibrated portable sacles, Much like the ones the diesel smokeys carry (in fact if you have a good friend who is a motor carrier officer or weighmaster.. That's an alternative)
Then they scale your rig, and hand you a piece of paper with the proper inlation pressures circled.. NOTE: They may be different depending on which wheel you are inflating.
OVER inflation.. (LIke running at the maximum pressure as far too man do) wears the center of the tread, gives a harder ride, ages the tire faster, and reduces your control in a bad situtation.
Under inflation, wears the outer tread, overheats the sidewalls, (leading to early tire failure) reduces your control but DOES, give a softer ride.
PROPER inflation, wears the tread evenly Is what the tire is designed to do, gives the BEST control in harsh conditions, Is to be desired. And for any given tire, that can be different depending on who's RV (Which RV) and which wheel on the RV.
So have it weighed.
You can also do it at any FLAT (not a bridge type) Scale.