a double leg is done with a hop step set up.......depends on what u want to do.....
to jump over something use the hop step.....but in martial arts tricks we use a setup using a roundhouse to double leg same as 540 like
there r two vry diff kicks doh.....for double leg its alot about upperbody......when u hop step.....run and do a lil hop....then punch into the ground with your feet. throw up your arms like mad to get some torque to bring your legs around
its all about upper body......
remember to throw those arms up in a circle to bring your feet around. once u get that the landing will come.....try not to overrotate, eventhough thats hard good luck
u need to try martial arts tricks
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oh and some dude said a 540 u go 360 thats not true u go 540 degrees jus some ppl dont do it rite.......u suppose to bring the landing right around 540 degrees
PEACE \V/