Oilspot:

Thanks for the info.  I guess my only concern about filling it to 50 PSI at no load would be what the pressure would rise to when there is a load.  I'm not worried about letting air out when it's at 55 or even 60 PSI,  but I wouldn't want to put the camper down on the tire and find that it brought it up to 70+ psi !

I was wondering if anyone knew how much additional pressure the load would add (approximately).  

Gary