This trick isnt as hard as it seams but required alot of guts and canot be messed up. I wouldnt advise trying this unless you have any kind of cussioning object liek sdnow or a mattress..

get alot of hight at first. when you swing backwrds get ready when you are almost as high as the swing will go  bend your knees back and swign the forwerds as hard as you can and lean back hard. after you are upsdie down let go of the chain and tuck up into a super tight ball and dont let go unti lyou are sure you have gone upsidedown two times. the worst that will happen if you do it right isl anding onyour stomach/knees.

The only videos of this trick are

Daniel Mahoney

parknastics

and colton B