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I disagree with it all being from the head - most of the goobers you see go upside down and stop are the ones that just throw their head back.
I was taught that you pop it from your hips and thighs. You thrust your hips up and forwards ("like you're smashing a hot chick", I was told...) and allow the motion to flow through your upper body so your shoulders and then head go back smoothly.
The tip about not throwing it until you're off the lip is a good one, if you huck it too soon (which is common when you're just learning them as everyone is terrified of scorpioning) you'll just be fighting the pop of your tails and also risk hitting the back of your head on the takeoff.