Chopsticks help!

Hey everyone! So I've been working on the chopsticks move for quite a while now, but I can't seem to get my back leg up straight and even with my front to form a flat split :( I'm very flexible in my splits and have oversplits on both sides, but can't get that darn back leg up to it looks all bobbly and crooked! I feel secure in the positioning, maybe I need to strengthen my glutes? I can do really good arabesques from dance, this is why I'm confused as why I can't get it! Help! thanks xo