Yes, hard to believe you would need more than Es. I have a C that is over-weight in the rear without anything added to go camping. Seems to have been built that way when they added the RV part to the "incomplete truck" they got from Ford to make an RV out of.
On the scales I got the true back weight when loaded as for camping and looked up the proper PSI for the four LT Es on the rear, and it is 65 lbs vs the 58 lbs the door label says the rears should be.
65 is no where near the 80 the Es can do, so how over-weight can you possibly be to need more than 80???? No way!
What are your scale weights?????