Just got mine over the weekend. Got the ultra for my 46# Fox recurve. I was a little leery because I ordered an SBD a year or two ago when they were still using D97 rather than the D10 they use now and I couldn't get that sucker to quit stretching. With a skinny strings you really have to make a lot of twists to make up any ground and I got to where I had it curled up like a spring and it was still too long.
Well, thought I'd give them another try, and this time I am very pleased. Brace height is staying put, it is quiet without any silencers and I can tell it is whipping my arrow quicker. No chrono proof, but I can definitely tell a difference. I think I'm going to try an SBD on my Blacktail and Rose Oak.