Sorry, but I don't have experience with them. I was lucky enough to find my crit group when member posted on a forum that's no longer active. If I were you, I'd start at the top and browse some of the forums. Then post in the one you think is the best fit. Oh, and you don't have to be a SCBWI member to join their forum.
Also, I'm not a Twitter person, but their might be some hashtags you could use to call out to other authors searching for crit groups.