The last time I had to source some it came from Aircraft Spruce. Mahogany ply for a Bellanca Viking wing repair.
I've been getting good ply from Hobby Lobby....I look it over pretty closely first though.
Once in a while I get light ply too but always hold it up to a light to look for voids...you can feel them too if you squeeze it.
Bill....watch that prop governor on the Viking....
One night I was taking my girlfriend to Boom Trenchard's Flarepath Restaurant at San Diego.
I was on downwind with it all hanging down and the stall warning screaming at me when I brought up the throttle and the prop went flat on me.
So there I was getting ready to hit a manhole cover in downtown San Diego and then i manually increased the pitch and we didn't die.
Scared the crap out of me...but I love the Viking....they fly remarkably great!!