Jon,
You are correct about the new bobbins. Instead of a point on the end they have a nubbin. Sometimes the nubbin is too blunt to fit into the hole in the spring loaded end of the winder. And some of the bobbins have rims that are just a bit smaller than the OEM bobbins so they fit farther into the drive end of the winder.
I have adjusted a couple of mine by gently bending the guide arm. It's pretty soft metal so I doubt it will break off.
But the adjustment has to be very precise or you just move the overfilling from one end to the other.
How do you make your own bobbins? That's interesting.
I have only OEM bobbins for my New Homes, and Minnesota. For my Free and Franklin I have both OEMs and reproductions. The OEMs are far better.
Joe