Teardrops n Tiny Travel Trailers

Been researching and can't seem to find the answer I'm looking for so I'll post my question here for feedback.

My exterior siding plans so far are Outside Plywood -> Epoxy -> Fiberglass Cloth and Epoxy -> Product such as Monstaliner. My concern is with the base plywood. I have seen people mention baltic birch for woody's as well as some other builds. Is this type of plywood entirely necessary for what my plans are, or would a hardwood plywood be sufficient as long as it's sealed and coated as I mentioned above.

P.S. This question was also posted in my build thread here.

--Metal

If you are going to have a smooth and painted finish, which I will assume, all you will need is a good quality plywood that has a exterior grade glue. I would find a lumber yard, not HD or Lowes, and ask them. You will pay slightly more but they get better stuff. MDF plywood might work and has a very smooth finish to start with.