Just curious, but why did you use marine plywood as the core material in your rebuild. Marine plywood is about the worst choice of core materials out there.
Many boats were built using it, but it was mostly due to cost considerations, not structural. Marine plywood is heavier than the other commonly used core materials, like end-grain balsa or foam, and it shares some of the worst characteristics of both. It rots like balsa does. It also allows water to delaminate large areas like foam does.
I'd also point out that if you had used either foam or an end-grain balsa based core material, like Baltek, you could have easily worked in larger sections than you were able to with marine plywood, as the materials are more flexible and would fit the cabintop shape better.
Nice job BTW... looking forward to seeing the photos.
There were 2 reasons I didn't use balsa. It flexes much more. The Merit has a very thin layer of FG on the cabin roof, and I wanted the extra support of having a wood that gave some additional structural support. I understand it's heavier than the other materials, but the water logged plywood was WAY heavier
the wet picture was taken a week after it rained. The other reason, as you mentioned, was cost. End grain balsa is not cheap. Foam is more expensive, and the exotic honey comb structure stuff is just stupid expensive. If I was building a boat from the ground up, sure, foam or honey comb would be my choice. I could budget for it, and justify the cost. But changing core material midship just didn't make much sense to me from a structural standpoint.
Thanks for the feedback everyone. I admit, these pics aren't the best, but I wanted to show that even a beginner can work with FG and get decent results. Certainly not like a pro, but good enough for my $1200 boat.