You're probably right, though I've never seen any voids in the Hoop Pine. It may be worthwhile getting a hardwood veneer plywood for dent resistance. Most of the strength of the panel comes from its thickness and the transverse grain layering of the plys so I don't think having hardwood throughout is such an advantage ( check the Kreige book for the theory on this).
I think it comes down to cosmetic resistance against the weight gain of marine ply which is maybe 30% heavier. My 14" Dob's Hooped pine mount sits out in all weathers..the estapol has long ago cracked and peeled off and the ply just seems to have seasoned itself and not really deteriating
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