Head Pass Variation
He doesn't sit up but stays low in stage 1. Extend him away to take his weight off of you, stuff the head to the side with your free arm and trap his head with your armpit over his neck. THREAD THAT ARM IN TO BEGIN THE KIMURA. Scoot your hip back towards his head to make it easy to get up on your elbow. Sit up on your elbow and grab the wrist as you lock the Kimura. Finish as before.
Jiu Jitsu Drill - BG shoots in, get a guillotine, pull guard and guillotine, stage 1 punch block, BG sits up with hands on the ground for basic variation or just stays there for the head pass variation.
Closing Statement: Let the opponent wear themselves out by throwing their initial barrage of punches before you attack with the Kimura so that they won't have as much energy to escape the lock. The key to the lock is trapping their arm with your top pulling arm since that is the arm that traps his arm in place. Once you set the Kimura, hold it tight, keep his arm bent at 90 degrees, and scoot out to get the proper angle for breaking his arm.