For a while I just wrapped the bungee around the spreaders, but that took a lot of time getting it on and off. So I decided to make it quicker. Sure, it gets in the way of the high bar, but that's also why it's removable and portable. You can click it on and off a dozen times a practice, and store it entirely out of the way during meets or rec classes. Also, you can have kids using the low bar for static shapes or holds (facing out) and maximize your work space.

For bigger kids, you can use smaller straps (and get more stretch out of the bungee, making it tighter). Or, you could just have a second set made of thicker, shorter bungee which would support their weight. Use whatever works best for the size of girl you train on cast-handstands.