My reach is long, but the power is not evenly distributed over the full motion path. It is that 80 cm where you most of the strength. The max power curve falls steeply beyond that point.
A 80 cm draw is for 20 cm rubber for a 5:1 ratio, correct?
My butterfly draw length measures 114 cm.
My guess is that your butterfly draw length is longer than 114 cm.
What is the initial rubber length in your powerful aluminum clad slingshot?
Using that rubber in a triggered rifle would be awesome.
I visualize a pouch holder/trigger made with hemispheres in a pliers arrangement that envelope the spherical ball inside the pouch.
On second thought, a hole on both sides of the pliers mechanism would be much easier to make.
Have you tried a shaped pouch and/or pouch holder?