Personally, I say wait a bit before using the collar. Too much pressure for seven months. There will be a time when the pup isn't going to listen and be stubborn and it looks like yours is starting. Slow down a bit. Alot of professional trainers won't start training until a year old. Its all well and fine to condition or prep a dog for training but real training at that age shouldn't involve serious correction. So, get frustrated.

If you start using an ecollar, remember the dog has to be conditioned to it. It has to know why it's being corrected and use it sparingly. As an example, my collar has a beeper and a stimulus range of 1-10. I've only needed to use a moderate rangeabout twice all season. Once when she went hunting for another group of hunters and wouldn't return and another because she was entering a restricted area and the beeper wouldnt turn her. Note, command first then beeper (no stimulus) then low setting (usually 2-3 times) then step up the stimulus. Off-season, the prongs get unscrewed so no stimulus.