AV8TOR,

Good point. But I wonder if location AND manipulation of heat range might not yield useful data. Say you're right that the incoming charge tends to cool off the plug at the intake position. So, you use the hotest plug you can find.

Or, alternately, positioned at the exhaust side, use the coldest plug you can get.

Mix and match differing positions and plug heat ranges. What might that reveal,, if anything?

In any case, a couple of hours work and nothing ventured till you try etc. Neat.