Buying the felt/fiber & punching your own sounds like the plan alright.
I wonder what the pressure difference would be between two identical loads (with the exact same shell, primer , powder & shot charge)...but one with the old school felt/fiber & one with the modern plastic wads?
I don't really hunt much, but like to roll my own for clays.
I could see how this could be very satisfying, where a smallish number of boxes were needed for your favorite birds.
Could be VERY tricky on a Progressive loader though!!!