Bowspirit,
I think they eliminated the solved the barbed problem when the redesigned the original screw-on interseptors and created the vented ones. Go back and look at the old original heads and I think you will see the difference.
Brack Shooter,
There is a recent posting of a Zipper/Tree Shark combination. Check out the doe in that posting.
Not to mention, James Wrenn has some mean pictures that show what a simmons head can do. And if your going to shoot carbons or aluminums, then don't be afraid of the schrew in heads. I've found that when using them I don't have to worry weather they spin true or not. They fly great.