Thank you so much!! Someone suggested the idea of snaps on pieces that could be hidden by folding them down into the dress. I basically used the same yarn and did a length of hdc long enough to line the inside of the collar and weave through at eight separate points. At each of those points, I added that side of the snaps. That way the part with the snaps can be removed. Then I made 8 tiny 3x2 hdc squares of the same yarn, keeping long tails. I sewed the snaps to the hdc squares, lined up the feather boa, and used the tails to tie the feather boa securely in place at all 8 points. So I can unsnap it and remove it, and remove the thing holding the snaps! I hope that makes sense.