I think part of the problem with things like chopsticks is that it's strength as well as flexibility to be able to pull your legs up into position (I guess it's strength in the hip flexors especially but maybe quads and/or hammies as well?). I have long had front and back splits and on a good day, could probably push to a bit of an oversplit on the ground when I have something to brace against but pulling up into a good chopsticks is a bit beyond me because (I think) my flexors aren't quite strong enough. My 2 cents worth anyway, not sure if this helps!