What do you mean by he takes off? Does he just continue to do his own thing, like hunting to the front; or does he run away entirely?
I've always started using the ecollar as a long arm of the law at the time my pups began ignoring a recall command. If they didn't respond immediately they got a little nick to remind them to obey. We worked on this intentionally, meaning free running and a few recalls were all we did in that session.
When they came to me, they got some atta boys and were sent on their way again. I did this because I didn't want them to figure out that obeying a recall meant the end to the fun.
Besides training in conditions where there were few distractions, I set them up with some temptations. Maybe with other people and noise and activity around, or when they got to chasing killdeers, or when they were going hellbent in one direction and I changed to another. Again, they got one command and a nick if they didn't respond immediately (in the field, remember it might take a second for your voice to reach them).
Besides working on recalls, I've found it helped to take them on lead to exciting places, and make them maintain focus on me. So no pulling me around on their leads, always correcting them for rudeness like jumping around or charging people or other dogs. Basically teaching them to be civilized in company.
You might want to take your pup to some events or group training sessions as observers and let him get used to the hubbub. Make him behave, no lunging, barking, or carrying on.
In my experience at tests and trial situations there are always people around who can help gather up a bonkers young dog. While it's embarrassing to you, it's something most participants have seen before and probably suffered through themselves.
Good luck and have fun at your test.
P.S. Make sure you have his county license tag plus your contact info tag on his regular collar. Just in case.
