Ok ummm lets see... I dare you to saddle up your horse and ride her BACKWARDS (sitting in the saddle, facing her butt, your back to her head) at the walk. If you feel comfortable at the trot, try that too.
Oh, I remember I did this at the canter once and ALMOST fell off... but I didnt.
IF you can't or don't want to do that then... stand in front of your horse, wrap your arms around her neck, and try to lift your feet up. (you will pretty much be hanging on her neck.)
Vegas used to let me hang ALL over him... he was da bomb. : )