Putting load range E tires on your trailer is NOT A MISTAKE. They will far outlast the lighter tire.
If you know the weight of your trailer while loaded for a trip go to this site and figure the correct tire pressure for your rig. Disregard the fact that the chart is Goodyear as all tires of a given size are spected to the same standards by the DOT. You can always use a tire with a higher rating.
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles