On my strip built Night Heron I've got a fixed fin, about 25mm deep, 40 cm long, located about 25cm behind the cockpit. It's wood core, with about 3 layers of 4oz s-glass, and epoxy/silica putty along the edge.

I might eventually put in a retractable skeg, but this has served me well for several years. I would not want it bigger and I definitely wouldn't want anything like a permanent skeg further aft. For me, an aft located permanent skeg would take way too much fun out of the boat. I'd feel like I was locked on a track. Maneuverability is a wonderful thing.