New perch going in today - how much space needed to fly down?

[Gullygarden]

Background to my inquiry into perches: a previous hen used to roost on the head-height clothes line in the garage. (really did wrap and hold with those toes) It was quite a surprise the first time to stumble in there in the dark and bump into a swinging white feathery shape at just above my head. She was a delight - laid regular eggs in the garage too. The kids didn't like it because they felt bad if they turned on the lights and woke her up. She instigated the building of various coops over the years. She was a flyer but this group of orpingtons don't seem like they will have the same capabilities and it is just as well, since now I keep them fenced, having lost too many to dogs over the years. So I have a new coop and the present roost is only 2 feet high across the back 6 foot side, with plenty of room to fly down. They've been sleeping on it on their own for sevreal weeks. However, the silly babies have recently taken to sleeping on the ledge on the long side, 4 feet up and with no room at all. They will soon be too big to sit there. I thought I might put a perch near that spot since they want to be on the light side of the coop, next to the clear plastic wall, instead of in the cozy dark back. I guess I can put the nesting boxes back there in the dark when we get them built, but the new location has no runway like the back perch did. By the time I go out 12 or 18 inches from the wall, the landing zone gets pretty steep and small in a 6 foot wide coop. Hence the questions. I was gonna build it today but we painted instead because we still haven't figured out what to do! Maybe just a low one over there, but they will just use it to climb up onto that ledge! Thoughts? I'm adding some pics here:
Existing perch, and the other end with notes showing whats going on and what I might do: