My dog goes in very fast during bitework and will pull hard as long as the handler is pulling on the leash. When the pressure is off, she loses interest. Help?

I have a 12 month old GSD female that I am gearing up for Schutzhund work. I refer to your excellent DVD's for inspiration, especially those by Bernhard Flinks, that I consider to lay the state-of-the-art ground rules for us.

My female, aka Chinook, is coming along very nicely except in one area: bite-work. Her tracking is very, very good. Her obedience is as good as I can expect in a 12 month old bitch, but her bite-work is worrying. She goes in very fast, whether on a cushion or a sleeve, pulls hard and holds in there, and as long as the handler is pulling on the leash. As soon as the pressure is off, or the helper slips the sleeve or lets go the cushion, she loses interest and lets it drop. She has no instinct to possess the prey item, let alone carry a sleeve or anything else back to the car or the crate.

The helper is very experienced and knowledgeable. I have also worked her on other helpers who dismiss her as 'needing her bite corrected' but so far, no deal. I can't help thinking that the genes are simply not there. I was very attentive to begin with and chose a very active pup (I had virtually the choice of the litter) but maybe I mistook hyperactivity for fearlessness. My helper doesn't think a bungee is the answer. His attitude seems to be 'Let's hope it fixes itself on its own'. I took my last dog, a male, up to a pretty good level in IPO 3 and he was a natural to bite-work. This problem has me stumped and I am thinking of maybe letting poor Chinook go. Any suggestions?

Tony