Here is an alternative concept for anyone who is interested.
The trailer is an 8x4 with extended drawbar that I built a few years ago.
i decided to build an enclosed box for extended travelling, but with a rack on top for the long stuff. I can fit 9' Mal inside but have to put the 10' Mal on the racks.
I also wanted to cary my trail bike so the front is a funny shape to clear the handlebars. Frame is welded square tube. Cladding is Colorbond sheet. Floor is plywood. I can quite easily slife the box out to use the tralier for other tasks, and haul it back in again with a small hand winch. It just bolts to trailer at each end. The tailgate just hangs on its chains when the box is in and I have to relocate the rego plate.
If I didn't want to carry the bike on the front, I would have put it forward over the front instead of out the back, or both so I would hold the 10 foot Mal.
Fits 4 boards easily with 6-8 sails and many masts, bases, fins, booms etc. Plus up to 8 Jerry cans of juice for crossing the Nallabor!




Before all the cross bar racks were in:

Somewhere down south in WA.

First big trip before I sorted the internal racks etc.