This may not be politcally correct, but my take on the SPA is it was setup by a few people who like to use 4-strokes and didn't like messing with retracts. That is why they allow alterations to the planes to use the 4-strokes. It has nothing to do with noise. It is still mostly a southeast region series. It's spreading a little but would really spread if they allowed the proper equipment of the time to be utilized. This is obviously my opinion and others will agree to disagree and that's okay. No malice meant by it. I like that something akin to the old pattern is taking hold in some form.

Jeff