I am with you. I have always stitched everything, vowing NO GLUE in my hats. However, I am starting to see that a drop of glue here and there is not a sin, when stitching alone will not do the trick.
The way I have fixed quills is by laying the quill in the place it touches on the hat in two places and bore a small hole through the shaft of the quill. This is where you attach the quill matching the thread colour to the quill and if needed a tiny spot of glue on the stitches . I suppose if the quill is very big it will need more holes in the shaft, this where you need use to your judgement. Good luck and keep stitch Evelyne
I try to make holes in the quill to stitch through, but beware once used a very small crochet hook to do it instead of the awl and managed to embed it in my finger. Was very nearly a trip to hospital, but without fainting did manage to get it out. lesson learnt and will only use awl from now on .
I have attached them by heating the needle and using this to push through the quill, a few stitches to fasten in a couple of places and a dab of glue. I was taught to use UHU glue on a millinery course as it doesn't discolour/turn yellow over time and its super cheap and easy to use!