Deck was epoxy-ed on the hull with a few layers of fiberglass (100g/m² and 50g/m²) on various spots that I deemed "critical".
Epoxy fillets were added virtually everywhere though I still might have to add a little more epoxy on the deck/hull joints. But the whole thing is already pretty strong.
Aluminium L and U profiles were added on exposed corners so as not the expose the cheap plywood.
Weight is 5.7kg (12.5lb) without ballast.
I took the barge and the trusty Sequana to the pond for the first tests on water.
Here's a lousy (cellphone) video from the trials.
I'm tempted to install two winches on the barge instead of using springs to keep tensions on the lines connecting the tug to the barge.
Run time suffered a bit of course. After close to two hours of sailing I experienced some voltage drop (remote switch for the lights reseting itself) and decided to call it quits.
Probably getting too close to the minimum voltage required by the ESC's BEC.
Obviously some finishing work still has to be done.