I would not be afraid to use that stuff for structural IF you have the right connections to other surfaces. Think of your ply as the sheet of paper on a sheet of gypsum board. It is merely a skin which prevents the tension forces of breaking the sheet, since you have one on each side, and tension is the strongest load bearing for most woods, this works out well to just use any thin skin and create a sandwich structure, whether it be foam, torsion box, or otherwise inside. Of course a rigid foam of sorts would be best (particularly if it is fully adhered rather than spot glued) because it then transfers all the sheer loading equally throughout the system and prevents point loading to break anything. In short, you could use rosin paper as your skin material of choice if you found a good way of sealing it (a thin layer of fiberglass perhaps) and had continuous bonding to the sandwich core (ccspf for example).
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