Thanks Shark Bait for your advice !!
I will be using this kayak mainly for day trips, but also I hope I'll be able to participate in a more ample event, descending on the Danube to the Black sea, which means probably one week.
SOF looks really fast after you've finished the woodwork and also skips the fiberglassing part which is unknown to me. Unfortunately the materials around here consist of pvc truck cover or pond liner, adhesives are also not so easy to find.
The most important aspect about SOF kayaks is that I would probably render it unusable very fast, since the Danube shores are littered with pieces of glass, wires or even "friendly" fishermen. So for me, 6mm okoume plywood is the minimal safe when I think about paddling on a big river like the Danube.
Buoyancy aids are also missing, so for a complete noob like myself this smells like disaster.
Thank you for the links, I partially read Tom Yost's site and it's a really fast tehnique .
Thanks !
Dan.