What is your opinion of training with groups?
Every trainer I know trains differently. They all have their systems that they like and follow closely. I live close to Tom and have visited with him a number of times his method is just that a method. Some guys mix methods and do well at that. The guys in the group you are training with have their own styles and methods. Train the way you like, a good training group will not force you into their methods, they may at time make suggestions but if they want to put you into a box, find another group. I am a believer in a check cord as well. My latest pup began to do things other than bring the dummy back to me at about 6-9 months. I put a check cord on her and never threw a dummy farther than the check cord. Then she was forced to always return to me. After 2 weeks she was back to longer retrieves because she understood the rules! If you follow a system to a T it should work for you. The only problem of not taking outside suggestions is that not every dog responds in the same way to the same methods. That is where someone with more experience with multiple dogs can help through those situations. Best of luck!
You can always look at Bill Hillman's youtube video's. He is a great resource on young dogs as well.