I belong to the Mt. Hood Miata Club and I know that the members love parade laps that are held at various events. I hope you make this a part of at least some of the events you hold. I especially like what they did down at Laguna Seca recently for the Miata 20th Anniversary event. The parade laps were not based on x number of laps but rather on a given time slot of about 1/2 hour. Some folks drove a few laps and came in and others sayed out the full 1/2 hour. It was great fun.
I also hope you occasionally offer hot laps. At PIR they offer these at almost all the races as a fund raiser for various charities. They usually use the pace cars but I've taken a hot lap in a Spec Miata and it was the thrill of a lifetime.
