The uniflex 255 is $87 a gallon. I believe you could do an entire Weekender with 1 gallon. But yes, you would want to put some epoxy resin under that. I used CPES, but really any thinned resin would work.
That squared trailer that you saw is my Weekender design. It was originally designed to go together in a weekend, or perhaps a long weekend. No one has ever built the design as I originally saw it, not even me. I built a lightweight versions with thin skins and sticks. Frank is going to finish building that one for himself! Here's the orignal design:
http://www.mikenchell.com/weekender/design.html
The original intent was for the panels to be 3/4" plywood glued and screwed together, painted with Uniflex 255 on the outside, and finished with stain and poly on the inside. The hatch, was really really simple, just a board! I built a mockup out of 1/2" OSB to validate my theory. Michelle and I built the whole thing in a morning one saturday! Here's the build photos:
http://www.mikenchell.com/weekender/mockup.html
Of course you couldn't build the real thing out of OSB. It would fall apart on the road. But a good plywood would be just fine!
I've played with many angled designs, and you're right, most of them don't look that good. If you want to build the squared weekender, this is the profile to use:
Have fun! Remember to take some photos and share them with us.
Mike...
P.S. If you start your build on Saturday morning, you might be done Sunday night. That doesn't include your trailer, or the painting of course!!! So what ya waiting for?

The quality is remembered long after the price is forgotten, so build your teardrop with the best materials...