Diamond Lake Announces Rules for the 2021 Slow Box Derby Though Brian and Janice Smith recently announced they are in the process of selling Diamond Lake Campground and Resort, they are still hard at work on the 2021 season, which features some new events for campers. One such event is the 2021 "Slow" Box Derby, which is an absolutely hilarious take on the classic Soap Box Derby. Yesterday, on Diamond Lake's official Facebook page, the Smith family published the rules for the event. Take a look! Diamond Lake As you can see, Rule #1 outlaws current, past or future Soap Box Derby cars. Naturally, those cars are built for aerodynamics and speed. That's the antithesis of a "Slow Box Derby." LOL.