My Penedesencas stayed in a six foot fence, but they never free-ranged either. My Buttercups were great at staying in their pen, but were great foragers. I got rid of my Dominiques because I couldn't keep them in a five foot fence. Even after clipping, they'd walk the wire, beating their wings until they cleared it. Surprisingly, I had some bantam Cochin cockerels that would also get out of a fence that was over six feet tall. Honestly I'd assumed that because of the way you raise yours, that if there were very confined they'd clear the fence in order to get out as they were used to more space.
I should also say that I've never equated the term "flighty" to mean actual flight out of an enclosure. After working with Light Mediterranean breeds flighty is just as you described. Although defining it mentally and seeing it in person can be two different things.