Matt explained it perfectly. Here's an example.....my cut is 3/4" to 3/8" 12" active. If I use that cut with 1mm elastic and shoot 3/8" steel it's gonna shoot 240ish with a hard draw and inconsistent accuracy. If I do that cut with .5 elastic it will be shooting well over 320 FPS and be a very accurate setup. That said if I'm using .5 lead, the .5 will shoot extremely slow and the 1mm will be still shooting 240ish and shooting consistently. And say I have something I can put wide bands the .5 cut 1.5 to 3/4 would probably be faster than the 1 mm.
With my setups I go as thin as I can before I start losing efficiency.
With my setups I go as thin as I can before I start losing efficiency.