According to Curt Gelin, the hull was good, but obviously, a 20’ hull which weights 800 kg is likely to be stronger than a 20’ hull which is only 400kg
My previous boat, Frøken Sørensen, weighed 740kg at 6.5m (no ballast). She surely felt as strong as a tank compared to a Fabola Campus, which felt really flimsy.
I note that a Hydra owner commented on that the transom was vibrating during motoring, so it may be on the thin side. My guess is that the outboard bracket has just been bolted on, without any backing plate, and that can be fixed easily. The best would be to have a good look at a Hydra. If no cracks around the keel or the rest of the hull is found, and if deck and cockpit surfaces feels stiff to step on after all those years, then it is probably all right.
Conclusion:
If you are mainly to thrash about in the Atlantic Ocean, a Hurley or that Gallion may be a better choice, but for the joy of sailing, the Hydra is an easy winner over these two.
Arne