We have had several questions about nibs (both Heritance and other upgrades), particularly with the Penn State pens.
I have to admit I have not used every pen, so I respond to the questions as best I can, then try to find that pen and do some experimenting. I did that with the full size Majestic and found that I needed to slightly modify the curve of the Heritance nib to get the best fit.
As we all know, the purpose of the nib and feed is to give good ink feed and a steady, reliable "lay down" of the ink. We also know every ink is a little different. So, what I do is compare the replacement nib with the original kit nib and see how I can adapt the replacement to make it more similar to the one designed for that particular kit.
At one time, about a year ago, I did significant work with Schmidt, hoping to have them build a nib and feed for kit pens. As it became clear that we could not generate the numbers (tens of thousands) to make this feasible, I suggested we would just buy the nibs and forget the feed. Their experts were STRONGLY opposed to that. They were adamant that the feed is an integral part of the "ink delivery system". So, the project was abandoned.
The Heritance nib was designed to fit the CSUSA Jr. Series. The curve of the nib was made to fit the feed that came with the kit. (Yes, I was involved in this--I know it is true) The remainder of the kits will be "hit and miss". IF they have a feed that is the same as the Juniors, the nib will fit "like it was made for it". If the feed is somewhat different, you may have to display some knowledge of "nib adaptation" to make it work properly.
One at a time, I will learn what kit pens are a simple pull out, and replace. I will "share" that knowledge, either on paper or youtube.
They continue to make new pens----I doubt the designers care about the difficulties it may create with nib replacements.
Hope this makes it a little clearer,
Ed