Since so many people here have lots of experience training their dogs at a high level, I'm hoping for some help in this little problem I'm having...
I started teaching my (almost) 9-month-old GSD pup to heel. He's already excellent with the sit, down, come, stay - obeys under distractions (doesn't get easily distracted anyway

) and always performs very quickly and enthusiastically. I very rarely have to correct him, as he's so eager to please and so focused.
I watched the Leerburg "Training competition heeling with Tom Rose" DVD many, many times (could probably quote the whole thing in my sleep, haha) and am precisely following the methods shown there to teach my dog to heel while maintaining eye contact.
So far, Tom's methods are working very well - I'm extremely impressed with the DVD, it covers each step so clearly and intelligently!
At the moment we're doing maybe 5-10 steps at a time (straight line, normal pace) and my pup will watch me intently as he heels at my side and will catch the food when I spit it out, just like the dogs on the DVD.
The problem: my pup is highly enthusiastic in his obedience with super drive (food & toy), which is great fun for both of us

, but he tends to jump up at me a lot while we heel.
In the beginning of the video, Tom says that one should NOT correct the dog for jumping up.
He says that we want that kind of enthusiasm from the dog and that the jumping up is "an easy thing to correct later on".
Unfortunately he never does go into how to correct this on the tape.
Now my pup is already in the 95-100 lbs. range at 9 months and when he jumps up, he actually reaches my face and will happily try to grab the food from my mouth (he stays in a perfect heel position the whole time though!).
I tried (using only a flat collar) to hold the leash in a way that would prevent him from jumping up, but as Tom warned in the video, this is causing my pup to lose some of his drive and to lag a bit. He's not even a soft dog, so I don't know why this would happen. I use a prong collar on him for the correction phases on other exercises and that doesn't seem to affect his drive at all.
(My guess is that he learned to back off when he feels pressure on the leash - I taught him since he was a pup to walk without pulling on the lead as shown by Ed in his basic obedience DVD).
Any suggestions as to how I can stop the crazy jumping without dampening my pup's enthusiasm? Heeling is a brand new exercise for him and I want to keep it all motivational until he learns it.
I'd be happy to ignore the jumping, but as I said, Taro is very strong and big and I don't want him to grab my face in his mouth or to knock me over