Your feathers are the shape I like. They are at a good angle from the spine. I usually say 45 degrees, not straight out or straight up. They have nice round ends and the feather comes back to the spin at a nice angle as if it could continue all the way down the spine. Keep going. And congrats on the longarm. I am going to post a photo in a few minutes so you can check out my feathers on the back of a quilt. It will be under Bonnie's quilt. You will find your feathers are like mine.
Another option for your deep curves: When you have a deep curve, you can piggy back feathers to get it filled and go around a really deep curve. Piggy backing is doing a smaller feather and then the next is larger and goes over the the top of the smaller feather and then the third is even longer and extends over the top of the second. It is just one way to handle a deep curve. There are many ways to deal with deep curves on stems. Try them all and pick what you like.
Feathers are an exciting journey. Congrats on the longarm.