Haven't had the time to post an update, but here it is.
deck is done:
435gr biax glass
200 twill carbon in the stance are + 300 UD as a stringer and as a nose protector
200gr twill glass
1.1kg of epoxy.

What I've learned is that 435gr is (for me) the max to wet out. It was hard to get the epoxy through the weave and probably as a result, it consumed a bit more than needed.
I've used epoxy from another brand and it was thicker too, but somehow felt better quality. However, the epoxy turned out yellow-ish, yuk!

Next will be sanding everything smooth, especially on the rails where the deck layer meets the bottom layer.
Then it's time to do the coating.

Currently the board comes in at 7.17kg which is much lighter than I expected to, so I hope it's strong enough. Similar construction production boards come in a 9.3-10.3kg. even after 2 layers of epoxy, it should be below those numbers. I expect an additional 1.5kg before it's finished.
Compressing with my thumbs probably isn't a good metric, but it feels solid (much more so than my first cork sandwich board). The stance area barely can't be compressed, the nose protector feels rock solid.

I haven't made up my mind yet on how I want this board to look, so shoot if you feel creative!
I was going for a white sanded look with some carbon shining through but there's no chance that'll look good now that the deck has a yellow-ish shine to it.

boardsurfr said..
Peculiar choice to use carbon for nose protection. I always thought carbon is more likely to crack than glass, and the noses of my slalom boards seem to confirm that .
Here's a picture of the wing board I just finished for my wife. Glass only, top has a sandwich layer of thick d-cell. Came in just below 7 kg, which is quite heavy for just 60 l.

Looks like a nice board! I think weight is much more relative to the dimensions of the board. For sure a board with the same weight but 30cm longer would feel a lot heavier when up and foiling.

It is indeed likely carbon will brake first on impact! In a composite, you always need to think where you want to use the different materials. From what I've heard, sandwiching it between glass layers is better than carbon + 2x glass for example. Also in case the carbon brakes, it's nice to have it more 'outside' so you access it more easily to repair it.
Anyway, it is within carbons' properties that it brakes before glass (less elongation). Carbon can take a big load, but once it brakes, it becomes completely useless. Diolen/ innegra are the opposite: takes little forces as it is super flexible, but almost impossible to brake. Glass sits somewhere in between.

At first I was thinking to go for 2-3 glass patches, but I felt adventurous so tried something different! Maybe the downside of glass would've been it being more likely to leave dings. Carbon will either resist the forces or the forces will slice through.
I think it will withstand the crashes of my freestyle sail just fine. Fully cammed sail will wrack anything! (Although, my patrik slalom board never broke after a crash, except for when I landed with my knee on the nose)

Nice to see you sorted out at the end. Please let us know how it goes; I am in the process of building my second board and I am curious about yours.

I always gave for granted thata sandwich construction would have been better: more lightweight, more rigid, more ding resistant, but I believe we need to think more about expecially for freeride foiling.
I made my own calculation, and costwise they are there if you use good materials, from craftmanship there is no competition, traditional layout is way easiereven though my comparison considers using the vacuum bag for both since I have it.
From ding resistance point of view traditional lay out is better,; simply more fibers and resin resistin an object to go through. from rigidity point of view we may debate: it is true that a sandwich has more flexural strenght the higher is the thickness, but we can't really compare the two constructions this way. The traditional one would imply more dense core EPS as you have used, and the skin have prox to 0 thikness so the beam is not the skin but the entire board and from local resistance to pressure sandwich is better for sure but from overall rigidity I guess they are pretty close, expecially if we put into the lamination good amount of good carbon fibers where needed.
The board is not slapping, so the problem of deck softening is less of an issue...it seems that the hassle do not justify the supposed increase in performance. Probably a traditional lay-up with foot stance 3 mm PVC would be the best compromise?

I have no absolute truth to state, just feed for thoughts for other 'builders' out there that would like to share their experience too.

Ciao

Edoardo