correct tire pressure

I use G tires and know from experience not to use max. The farm coop in Ft. Collins, CO told me these tires are good for loads of about 25,000 lbs. A vacation 5th wheel is far from that. I was loading the tires to 110 and the installer climbed all over me. He said I should start at 85 go lower and he anticipated 80 was good for me. I have been running 85 and I see a gap on the outer edge. I am reducing to 80 next trip. I am 12,877 dry and carry 10 gal of water, keep the waste tanks low and carry tools and clothes. I guess I am 14,000.