Hi Duane, please reread my post. My point is that the non-legal, post '76 designs that I cited could, in fact, be at a disadvantage to early '70s designs when using the same side exhaust, non-piped sixties. The three planes I listed are all after the SPA cutoff, are larger and were designed around more powerful piped RE sixties.

To put it another way... suppose the SPA cutoff was 1980. But, you were still limited to using a side exhaust, non-piped sixty. I'll bet most pilots would still choose to build the smaller, lighter designs of the early '70s. So, having the '75 cutoff doesn't really "level" the field that much, does it? Image trying to compete with a contemporary 2M design using an older 120 4-stroke. You just don't see people doing that. Why? Because the latest pattern models have been designed to fly with the power of 140's and 170's.

Thanks,
David