I made a post yesterday RE: the $54 Bower adapter ring vs. the $270 Novoflex ring. It required 2 people to get the Bower ring off of my AI'd 50mm prime. Once removed however, I attached the ring to my 20mm f/3.5 AI and the aperture clicks with perfect smoothness, easy to attach/detatch, etc.
I think these rings might be exponentially more difficult to use with AI'd lenses, rather than the factory-built AI or AI-S lens, which is what my 20mm is.
If you go the route that I do and use older Nikon primes on your 5D/7D/T2i--- save yourself some cash and use the Bower brand.