What about stacking the top one inside the bed of the lower one with it's tires / wheels removed.
A 4x4 or 6x6 saw horse on the wheel well with lateral bracing may work if the axle with hubs wiill fit inside.
It would work pretty well, would probably be more agreeable to by GL loaders, and would be more easily unloaded once it arrived home since it is right side up.
It would still need to be strapped down but much more stable and would hold up to sharp braking due to "goof balls" being on the road at the same time.
I'm going to measure the hub to hub dimension and report back. I could not find it in the TM9-2339-213-14&P.
Note: The empty trailer weighs 2694 lbs. per the same TM above with side boards and cover installed so that is a lot of weight to tow X 2 on the hitch not that it can't be done safely but unless a deuce is pulling the lower one there are no brakes to be had while behind a civy truck.
jimm1009
Edit for additional information;
I removed one tire and measured the width of the drum as shown in the PDF drawing from the TM. The ring of nuts on the drum (approximately 20 nuts) is where I measure to and this dimension is 67 inches from side to side. The backing plate to backing plate is 56 1/2 inches wide.
The very outside to outside dimension was not check because it exceed the width of the trailer bed.
What my pea-brain came up with was to set the trailer inside the other one right side up with the tires removed. The drums would fit inside the total bed width and they could rest on a wooden or steel brace that rested on the wheel well and floor combined. The tongue could rest on the forward wall of the lower trailer and be strapped in place there.
GL may be inclined to use a fork lift to lift is straight up and then set it down since this is a very simple maneuver.
See PDF. There is about 3 1/2 inches difference is the diameter of the brake drum and the spndile diameter but that shoule be enough to work if so inclined.