I also would sand the joint for a well mated surface.

When you have some time on your hands, try this. Mix a small amount of epoxy (5, 30, or whatever) and just let it harden on a plastic lid overnight. Also glue two pieced of light ply together with the same stuff. Next day, try and get the light ply apart. You won't. Now try and break the spot of epoxy. See how easy it is to break when by itself.

Point is, the strength of the joint comes from a tight fit of the two surfaces with the epoxy reaching into the fiber of the wood and kind of welding the pieces together. Gaps weaken the joint, because all that is holding it is the brittle epoxy. Over time, this joint will develop cracks, unless backed with a layer of glass, as mentioned above. I little sanding to make a machine like fit, and then glued properly with epoxy, will make a strong, lightweight joint. Always make sure you are gluing wood to wood also. Always remove any covering in the way of the joint. Otherwise, the joint is as strong as the bond of the covering to the wood. Not very.