I went through a video series called Feather Boot Camp and she has you do a LOT of drawing. You might like it.
I'm no expert, in fact I'm taking a class next week to work on this, but I've seen people do the length of the quilt and join then in the centre, making the curve of the spine match on either side.
For myself, I find the "bump back" feathers tend to be more symmetrical when I do them than others. But, they are never really perfect and I think that's good.
Watson