Steve,
MDO: I've been using it since 1984. When cutting it with a jigsaw on curves, I would occasionally find a small void. I filled voids with Bondo. I used to paint MDO with automotive acrylic enamel, just a sealer coat first, no primer. As signs, the stuff lasted longer than all the businesses I made them for. Not kidding...over a decade. Hanging outside for years in the 100 degree plus summers and the below freezing fog, they never delaminated or got chalky oxidation. The paint would eventually flake off the Bondo on the edges, but never off the paper face. I decided that that characteristic would make for great exterior skin for a painted RV (and later a teardrop), so I used it.
I'd build a chuck box / camp cooking box with legs out of it also. It's so much cleaner than exposed grain on regular plywood. It would make a super smooth wall for a cargo trailer's interior also. It's just a little heavier than junk plywood of the same thickness.
One last thing: MDO is not to be confused with HDO. High Density Overlay is used for signs in very rough weather places (and for beefier concrete casting forms). I've seen it used for signs in Barrow, Alaska, Seattle and Mystic, Connecticut. It's got more laminations and is compressed much more than MDO...so it's heavier.
Prem
My goal...
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...is to live in a trailer.