I suspect the issue with keeping the trailer at 8'6" max width is that the reinforcement needed for the sides/ceiling would impinge upon the interior width, so your 8'6" cat wouldn't fit.
Unless you "jake-i-fied" the trailer so your cat slides out from the side where there would be no supports needed.. They'd be on the four corners or just ahead/aft of the hulls and crossways along the ceiling.
So maybe an 8'6" width by 22 ft. to accommodate the frame members and a roll-up door on the side? And maybe rails (or an overhead gantry type thing) to slide the hulls out laterally (where the beach wheels would be sitting).
Oh yeah, it all works out great in my imagination....
8'6" is maximum legal vehicle width in most of the US and to be within that, the interior space will be a little narrower due to the width of the trailer walls. The A-cat is only 7.5' wide so it would work within a trailer like that.
Any wider than 8'6" will require a wide load permit and, in some places like the Florida Keys, a hired police escort and only in the middle of the night.
I've had previous, road haze driving for daze induced, thoughts of a sliding rack/hoist system where a rod extension on rollers would slide out the back of the trailer, hook up a lift one side of an F18 putting it in the air sideways and slide it into the trailer like a tie rack in a closet.
