Yes it can be done, just seal everything really well. I did it twice so far and am working on a third. The first boat lasted a few years, it had some leaks that discolorated parts of the hull, and developed dark spots at several S&G holes. By that time I was done with it and gave it away. It was still strong and could have been painted. The second one worked better, I did a better job of sealing and had plugged the S&G holes with eposxy putty. No leakages so far after four years. When you scratch your hull, check it and fix it, don't wait. Still, marine plywood costs relatively little extra and even when leaks develop, it will not spread. It is worth the money for the amount of time you put into it. But again, it can be done just do a near-perfect job of sealing everything.

Henk