[aldo]

I used Nidacore also on my 23 inboard. If you search my user name you will find a thread called "Soggy Floor, Need Help" from a few months ago. I posted pictures and plans. If you are interested, I'll post the updated info of what I ended up doing. - I was on the right track but got some professional advice and help and it really worked out well.
Incredibly light& strong-did it with 3 pieces of 2'x4' nida core and some 5/4 mahogany.
I would need a refresher on posting the pics, though. Good luck with yours.