Chris,
The HT Class had a trailor that stacked 6 HT's fully beamed up and with tramps on. The towers bolted down to the floor and were made out of steel. The whole trailor was very heavy and pretty hard to load. The upper boats took 4 people to load.

I cant seem to find a picture of that trailor.

My opinion is that its easier to take boats apart if you are driving to FL during the winter.

If I were going to do it, I'd make the have floor, and a aluminum frame to hold the boats, and a outer frame and then stretch a rubber/plastic material over it to keep everything clean.

Kind of like the car carriers that have soft sides.

Bill