I agree with Chris Davison regarding the AC4. Our club owned one for about 9 years and I flew it for about 100 hours. It is wonderful little glider and I loved flying it, but it is rather delicate and does not do well in a club atmosphere. Ours got banged up in off field landings and a couple of ground loops. Understanding the construction and light weight, like Chris Davison, I'd be worried about motor induced vibration too. However, it still a great little glider and I believe there are over 40 flying in the US.

Chuck Zabinski