Print out, remove the support from the slide, test fit with the Fly6. It should be a little difficult to slide home so that it doesn't fly off but not really tight.

I ALWAYS recommend secondary tethering of gadgets. You can do it on the Fly6 by pulling out one of the rubber stops on the back of the unit, removing a screw from the hole, then putting a piece of sturdy line around the screw and replacing it and the stopper.

I use Spectra heavy fishing line (80 pound test).

Tie off somewhere. Don't give it too much slack or it could swing into the spokes and cause a crash. You can check my other designs for a suitable clip if you want to use that.