Yes, Al. If the engine is tuned correctly, the heat range of the spark plug didn't make much (if any) difference on the dyno. For extended runs on the track, however, the hotter heat range plugs continued to build cylinder head temp, whereas the colder plugs leveled off sooner. Again, the compression is so extremely low in these engines (about 6 - 6.5:1) that I don't think you'll see much going on there in the short time they're under load on the dyno. We, instead, manipulate the on-track temperature of the engine with the plug heat range (right or wrong.)
I've discussed on here before how we throw a bunch of ignition timing advance to our restrictor plate engines, dump tons of fuel to it, then try to light it with a hot plug (and still have to tape the fan shroud completely off to build any cylinder head temp at all.) The egt. runs between 8-900*F to make peak power on these small plate flathead engines. If we tune them to an "optimum" egt, it flat kills the power on them. It's an anomaly that we deal with on almost a daily basis with these small plate flathead engines. I certainly have my own theories and conjecture about the "why," but data and experience back up what's occurring. That's good enough for me to accept it and move on.