My ig was big when I used this method, and a few of his high speed dashed proved this leash works well. You know, igs and hutch-raised rabbits have something in common. Both are naturally gifted high-speed runners, yet both when raised in cages don't know how to make long distance runs. I had a rabbit who outside his hutch could only make a few hops in any given direction, and this iguana took a while to learn how to really make a run for it.
I remember now that I thought the long lead was a safety measure in case it slipped out of my hand during a dash. I figured I could trace his location with it wherever he stopped to hide, even in dense brush.