Hi Tony
Yes there is a secret Practice Practice Practice and more Practice
The art to a straddle is to kick the legs out hard so they spring back in
The best way to practice is on a trampoline or on your feet to get the right tecnnique before you go for it on stilts (I can do a better straddle on the floor than on stilts)
I would tend to try simpler tricks first like just trying to slap your ankles with your hands (like crouching down on the floor)
This wil get you used to getting your feet down in time
Watch all the vids of meets and people doing tricks and you can watch how they do it and copy the simpler tricks
Jason