Oh our GLW are full sized definately, for the bigger eggs...& this coming weekend they'll be 4 months; so they can still fly pretty good for beign about half grown. Our dominique has short wings & she seems to be able to fly straight up on the roost from right underneath it, bout 4.5 ft up, I think she just likes to show off though.
The wyandottes will not be able to fly over a 4 ft fence when full grown, as long as they cannot perch on it. I would think same is true for the doms, though I've never had them. Getting up to the roost is easy because they can hop/fly onto a sturdy perch - that's easier than actually flying over a wire fence.