Quail flight safety

My flight safety strategy for my coturnix quail so far has been one of flight avoidance. I've built 8-10" breeder cages with plywood top. From articles on this site, this is a good height to avoid injuries. Since I am raising them for meat and eggs, this meets my needs. I don't need them to fly, just to get fat and lay eggs.

My neighbor, who plans to raise some of next hatch for pets, asked about
cages or pens that are safe for flight.

So if one used netting for the top, what size cages or pens would be safe for flight? Note this is in a suburban neighborhood, so there isn't much change of building a 120' x 15' x 10' flight pen and getting game preserve ready birds. A 20' x 3' x 7' pen might be possible though, to allow the birds some exercise and hopefully avoid injuries.

These issues might also be relevant for me when building quail tractors or raising valley quail in the future.

Nathan