How about a Challenge-your-buddy link, one that sends a pre-formatted email to a buddy showing them how to set-up and play?
Have we ever looked into setting up an NHL94 server, as getting guys set-up on server would remove the step of needing Hamachi? It would at least get them playing quicker, with less set-up.
Maybe we need to create an over-arching website/forum for all of retro sports, Tecmo, NHL93/94/95, RBI and hitch our wagons together.