When you opponent has his legs crossed and is sitting low on your body, do the following:

Extend one of your legs fully and drive it to the ground seperating his two legs.  You may have to rotate on your hips to wedge it in.

Push off his hips and shrimp your legs out from between his legs.

Notes

1. Get a very high mount with your knees under his arm pits if possible.
2. Wrap up an arm with an overhook and slide your knee  towards his head on the same side.
3. Get wrist control of the other arm and push it to the matt.
4. Sneak your other leg up and over the opposite arm.
5. Pull body towards you with overhook and while maintaining wrist control, slide leg under head and cinching the choke.

This is a nice “baiting” move to get it started easily (untried):

Notes

• If the arm is not in a position to turn and put it in front of his face, I can hook it with my right arm spinning across while mounting.
• Once I finish spinning, I will grab the crown to hold the arm above his head.
• Now feed my other arm underneath his neck and grab his armpit to help secure the arm.
• Bump the arm underneath his chin as fast as possible and hug it with the side of your head – your temple to his temple.  Once secured, go to knee-on-belly and squeeze and drive the knee.

Another way to get it (untried):

Notes

• Start by getting wrist control like I am going for a kimura.  That will keep him from basing out on his arm and preventing the sweep.
• The sweep actually is off to the side at about 45 degrees – not straight back.
• Throw your opposite arm across his face over his opposite shoulder.
• Try to hip bump really high into his chest – and drive your knee into his armpit.

If unsuccessful, try to come down into omoplata (untried as of yet):

Notes

• Must be sitting on shoulder and watching his legs.
• If he gable grips your right leg, you can triangle his arm and get a baby arm-bar.
• Grab toes and sneak foot across belly for mount.