No one in there right mind would think of pack extenders.

Most of the flies try to bite on the head.  A wide brimmed hat with permethrin on top really cuts down on the bites. I was in the canoe with Kingfisher.  He was wearing a base ball hat and I had a wide brimmed hat on.  I did not even know the flyes were a problem and he was bleeding on his nick where they had bitten him. He said there was many circling my head and they would land on top of my hat but I never got a bight.  Does not work for ankle biters.
MagicPaddler