Good advice from BigCliff, those bugger packs are ideal. I didn't think of what WT mentioned, but a dubbing loop would also work.
Another idea, have you tried tying them in tip first and wrap up the shank to the eye? You might find some smaller barbs at the tip of the feather and then by the time you get to the eye, you've got some big ones for a collar.
I sometimes like a larger hackle on buggers, how big is too big? Can you post a photo of one tied up?
Google is your friend: