When you said you took ALL the plywood out of the boat, anyone reading your post was right to assume you meant ALL the plywood. Like the bulkheads.
If all you're talking about is some quarter inch paneling, that's another matter entirely. By the way, some clarity would have been useful.
You're still probably going to be well served with epoxy, as it will give a tough, waterproof bond without needing a lot of clamping.
You could use something like a one part glue, but you'd probably have trouble exerting enough clamping pressure. Also, you can rely on epoxy giving you a good bond to both fiberglass and wood. It's not hard to work with.