I have seen the Meng perch used without any problems for about 6 years now. One of the guys up here has always used them for his Gos. I'll throw up a good picture when I get a chance.
Here is the picture. Its not as good as good a picture as I thought but you can see where the leash is attached. If you can put a Gos on it I can't see why you couldn't use it for a Redtail.
The bars in the center are important they keep the bird from getting tangled up on the perch but perhaps you addressed this in your design, cant wait to see the pics
These perches were peddled by Northwoods back in 1988 and he also made a falcon spike with a similar philosophy credited to Heinz Meng. I'm not a Shinto-Falconer willing to give in to ancestor falconer worship. Heinz is a nice fellow but the perch is an unsafe design and I am not aware that Heinz has any reasonable credentials working with and keeping hunting accipiters in good feather. (maybe he has, but I am not sure)
Bringing the ring up the bow allows the bird to bate down with the leash pummeling the tail train of the hawk. On a good bate maybe it will allow the swivel to grind into the tail of the hawk at the same time.
This is one of those situations where there was no problem to begin with and Unnecessity was the bastard of invention. Bow perches worked just fine for 2000 years for the greatest accipiter and eagle falconers that ever lived...yet here we are with a weird perch that damages trains made by Heinz Meng as an improvement.
Call Brad Wood at Northwoods. For years in the early 90s he was trying to cut deals on these reject perches he pulled from his catalog. He took mine back for a full refund as he did others. I bet he has a few left on a shelf somewhere that he'd clearance out to a new owner unless he scrapped them altogether.