I would think cables or power bands, or even chains would increase resistance as the arm goes past level.
I do "get" that once you go past level, the resistance drops, but if you only go to that point, wouldn't that affect your range of motion as your delts get developed?
Hence, musclebound?
Also, even if you are no longer getting maximum contraction, (meaning you have achieved max contraction, and now the power curve lessens)aren't you still developing the delts more completely?