I would cut some scraps various widths and experiment before cutting the binding strips. I googled "fatt batt" online and it says 1/2" to 5/8" thick. Maybe you can stack up some thinner batting scraps and test out with scraps before cutting your strips. I generally use 2-1/2" myself on either warm & natural or Hobbs 80/20. I think I'd try a few somewhere between 2-1/2" and 3-1/2" and see which gives you the look you want.