Our club has never done anything to increase participation, it just moves guys from one class to another. SCCA's policy has been "Screw Peter to Pay Paul".
A couple of decades ago, SCCA's CRB brain trust opened up Prod to roofed cars. It didn't seem like a big deal, but it removed the feeder cars (the tin tops) from GT4/5. That had a major impact on small GT, because they went to Prod instead. CRB idiots said Prod cars would serve as feeders for GT, but we know that didn't prove true.
Think about E, F, & HProd today if it only included the original roadster type bodies?? Fields would be small, eh? [A decade later when GT asked to include roadsters, $hit hit the fan.]
So, joke all you want about your GTL brothers wanting to join Prod, but remember it was our feeder cars that sparked the growth of Prod.
Peter