Yes, part of the tuning will be reducing the weight of the springs, somewhat. The feather spring will be reduced in weight until it's right, then the mainspring reduced, in weight, to balance.
In reading the thread on the Muzzleloader Mag site, it was suggested that material be removed from the width of a spring, rather than from the thickness.
IMHO, a wider, thin spring is more durable and flexible than a thick, narrow one.
One DOES need to be careful about removing too much material from the thickness of a spring, but IMHO, it's the best way to go.
The poster on MLM site filed a wider bevel on the bottom of the mainspring. IMHO, that is probably the best way to go, for someone who doesn't know what they are doing. I will probably begin by grinding a wider bevel on each spring, then go from there.
I might even temper the springs, as per Jerry's instructions. Can't go too far wrong with Jerry's instructions. Shoulda done it long ago.
Thanks and God bless