Don't see why a dog has to be off the slip for it to jump a fence or gate, why can't it jump when it's still on the slip.
Must say it's a lot easier if a dog is working without a slip. I find it fairly easy to train them to do that when they're working solo, not so easy when they're out working with another dog.
When your carrying a lamp and battery and have a dog on the slip and need to get over a fence or barbed wire it's best to keep the dog on the slip?
I think that's making things very difficult to be honest !