Hi Dave,
The OS plugs were supplied to me by Japanman at the time he sent me the pieces he made. I was unaware of the super hot P3. I found the medium to simply work the best along with the trumpet or the stock head shape. The hemi was the worst one of the lot,, but I only took a guess at the volume. It would take an afternoon of adding/deleting shims while running all four plugs on various nitro fuels and LOTs of data recording to make a proper scientifically valid determination as to the best plug to use. And of course, if you add or delete shims to adjust for volume, you're changing the squish band and well, there's another variable to consider. I can see that one could make up four hemi buttons with varying hemi volume and then, do multiple runs while adjusting shims. Add to that, experimenting with heat ranges and differing nitro content and well, LOTS of R&D fun with lots of data to crunch.
I fried my P6 (hot) and I recall that it did well. Went the next up, P7 and it works fine. The P8 sounded a bit off, but I never really made any radical needle adjustments. These days, (summer) I get a bit lazy and just go for it if something works.
I'm going to get the two in the ranges that I'm missing and do a thorough evaluation of the usefullness of each, one day, on my new .074. This WILL have to wait till the fall though. That sunny, warm weather beckons,,, you know 6 months of winter,, got a lot of fresh air, sunshine and flying, beach and fishing to catch up on.
Crazy thing is, I look for a rainy day so I can catch up on shop work. Go figure..
