Captain K
Your sandwich panels keep haunting me. Not in a bad way from your perspective, but in so much as I have this 'overweight' fear stemming from all of the baltic birch I used in my remodel. early on I hedged my bets for strength rather than weight. As time progressed and things continually evolve I sometimes fear the cumulative weight of all the built-ins will have a negative impact on trim, speed and carrying capacity of stores.
So now I'm seriously considering how I should approach the 'revamping' of my remodel. I will be looking at where we can use some sandwich panels to lighten things up a bit. Because there are so few remaining bulkheads and dividers left to go in it will be a challenge. So in your spare time maybe you could peruse the photos of 113's interior and offer up some suggestions.
But! I did manage to find some photos of panels made for use in Baltic Yachts. You know by now that I'm a picture kind of guy.