No stirrups !! If your leg is swinging back it’s normally a sign of you gripping with your knees instead of your lower leg which means you’re not as balanced as you should be. I don’t recommend throwing your leg forward before the jump because that also puts your balance in the wrong place. If you do grid/gymnastic exercises with no stirrups, that’ll help a lot. But even just no stirrups on the flat will help a lot!