This is how you ride a girl. Mount her back or mount her ass. No legs behind legs. Straddle the hips and the butt and push. Tug her hair and spank her to move her hips on her own, and she's giving you a ride with her ass. Keep your feet at her hips while upon her back- have her crawl instead....or mount the ass, and have her crawl violated. She'll thank you eventually.