It will end up under 50 kg but not that much. I have very little experience in foam building and the foam is eating a lot of epoxy...

Try brushing on a layer and letting it kick before putting on the actual laminate. Or wetout and squeeggee your cloth off the part and then lay it on, the foam shouldn't wick resin out of the glass if you have the right amount there.

Do you know how much resin you used on the DS?

Squeegee a thin bog of honey consistency on the foam right before glassing. No need to let it cure, glass straight onto the wet bog. This will require "half" as much resin.

Thanks for the advises!!! The epoxy for the DS12, yes I have it written somewhere, will try to find it when I get back to the workshop.

The filler works,using peelply helps with weight to (shower curtain nylon works well)bill

The 4 halves are joined together, now it's up to the Nice Lady if we get some pics...

Gato, do you ever sleep ?
As this is actually a retorical question, judging by your activity - then the most interesting question is: how do you do it ?
Now seriously, great work !!!

How do you find working with foam compared to wood/plywood ?

The trick is; A bad carpenter has to cut a plank 3 times before it's to short, a good one does it at once...
Working with foam is great, fast, giving a good result and the cost is about the same. In fact for the moment I don't see the reason why to work with ply.

You can not enjoy the smell of wood, and the pleasure of using your plane with foam

Can you buy sheets of foam, or do you have to buy a whole package.

Well, the okume ply dosen't smell so good, it would be different if you built a real wooden boat.
As for the foam, you can buy a single sheet. I will try to get some pics for Monday.