I was going to suggest what Aly said, to step on the leash. I first learned about it on "Good Dog!" (Dr. Stanley Coren's show). It worked for the determined Pit Bullx so it should be no problem for Major since he's still small and hasn't been jumping up for as long.

A funny story about my experience with my jumpy dogs.. I had a friend over once who isn't too fond of dogs. Kai usually runs up to sniff the person and will jump now and then. She immediately yelled "Kai, down!" while he was sniffing and jumped up once. So he immediately layed down but kept sniffing enthusiastically while she kept screaming "down! down!" LOL