Something you might consider is modifing a pop up tent trailer they are light and can hold pretty much stuff. I know some racers in Texas use one for the Internats.
OOPPS jsut saw Marks post he beat me to it.
My son & I have a 4 x 6 and we have it setup for 5 boats including gas & nitro. We bought it new from a reliable trailer dealer in NJ and he sold us the following additions to the basic trailer.
1) Spare tire mounted on the trailer bar.
2) a hard rubber floor covering that is impervious to rotting, oil or gas spills, etc. and can be washed out easily.
3) zerk fitted wheel bearings to grease wheel bearings easily.
4) 13" tires so car travels easily. We are towing it bewhind a small Honda CRV with no problem whatever.
5) we fitted the insides with closet maid wire shelves that are detachable and moveable so we can change configurations easily. These wire shelves permit us to tie down each boat with simple bungee cords so they don't bounce around.
6) A metal stone guard on the front to prevent denting the trailer from kicked up stones.
7) A kickup third wheel mounted on ther tongue so you can maneuver the trailer easily and don't have to rest the tongue on the ground. It alsd keeps the trailer lever while at a racesite
While everything is tight (we carry extrensive toolboxes, spare parts boxes, two foldup tables. folding chairs, an easy up and an ice chest.)
There is an advantage in that nothing bounces around.
We still get decent mileage even going 65 miles per hour on highways with no swaying or bouncing.
hope this info is of help