This is probably old news but I've read about the problem.
The lil choppers want to roll over the tip of the feather when it cuts the base. This gives the cut feather an ugly hump in the front.
I have just got done chopping my first feathers for my first attempt at assembling some arrows.
I cut a few and had the bump. So I made a little holder to press down on the feather while it was being cut. I made it out of a popsicle stick and glued on a handle...didn't help much.
Sooooo I thought to myself.." you dummy, the reason it's rolling over is because you're cutting the base..quit cutting the base"
I found that if you take your full length feather and cut the very front of the base at a 60˚ angle or so ( just to make it pointed and look nice ) you can then slide the feather base right up to the inside of the blade. This way you don't cut the front of the base and NO ROLL = NO HUMP.
The chopper still cuts the back through the base but since it is taller it stays put pretty well.
Might be old news to you all but I thought I'd pass it on just in case.
Good hunting