I just read this entire thread (I hadn't before because with so many replies I figured it was sure to have drifted off-topic; happily, I was wrong).
1. You have convinced me that the trailer, not the TV, is the problem -- You've towed it with a variety of vehicles from a Neon to an F250, plus the muscle car, and the problem stays.
2. Without heat on the metal running gear (hubs/bearings), it is extremely unlikely that the problem is there.
3. With the extra height you have, presuming you are towing level, I doubt there is any "air dam" effect holding the egg back.
4. I don't believe weight, by itself, is the culprit -- Joy on Yahoo Scampers is running her 13' (dunno the year) weighing
2,200 lbs on a Dexter #9 rubbered at 2,200 lbs and reports no problems of this nature.
5. I sense Brian B-P is right that there is an axle misalignment problem affecting the tires and creating drag, altho as Scamp points out, the cupping wear is on the wrong side of the tire for overload. My recommendation would be to take the rig AS-IS, before any more new gear is added, to a true axle and frame shop and let them have at it -- They have the frames and gear to do the precise measurements and can maybe even do the bending required if the axle can be adjusted.
6. Before I went to the axle shop, however, I would try Nick's "How well does it coast in neutral on flat pavement" idea. That takes the tow vehicle almost completely out of the picture (except for its own rolling resistance).
I would suspect that if there is an alignment problem of any sort, the larger tires may magnify the fault. Regardless, if alignment is a problem, I would expect it to show up in hot tires.
The axle tag might be on the other side of the axle beam; it is usually riveted on. Sometimes the capacity is also painted or stenciled on the beam. My 91S13 came with less than a 2,200 lb axle (I believe it was 1,600, but I didn't keep the old tag...). Scamp should be able to tell you precisely what axle went on by reference to your VIN
and their records which were reportedly not damaged by the fire -- I dunno when they started using 2,200 lb axles as standard on the S13.
I believe Scamp is now using Al-Ko axles under the 16'/19' models because of alignment problems with Dexter #10 axles. Casita
had at least one problem with a Dexter #10 axle failing on one side.
Keep in mind that if your axle is undersized and you decide to replace it, the least expensive way to get brake parts (including the drums you want) is to order them with a new axle.
Don't forget to provide feedback, even negative results, to both the group and to Kent and crew -- The more we all learn, the better we are able to help ourselves and others.