NFP, I read your post but don't know a bunch about stihls so I kept my mouth shut. I've just read your post as well about your bar tip.
In that post you said that Mike Rupley found it for you. Well if you need the info on the 66 he should be able to help you as well. If he can't his brother sure can. He also rebuilds and hops them up as well. They both run hotsaws so they know first hand about heat and how to get rid of it.
The last 28" bar a bought off of Mike made me really laugh when I opened the box. He had it painted black with a number three painted on it. A class act.

But if you want my two cents on the 066 the cheapest and smartest thing to do if she is running too hot is to adjust the carb. On the high setting turn out until she starts to four cycle then turn it in 1/16 of a turn this will put it alittle rich. A lean running saw runs too darn hot and to hot explodes. Make sure the cooling fins are clean as well. Blow off with airhose.
Also on the muffler you can take away some of the backpressure but it's good to have some. The reason there is so much more on todays saws is because of emissions. So you could alter the muffler as well. Drill a couple of holes in it to relieve some of that pressure, rip out the guts, cut another port in it.----- Now a disclaimer, if you blow up your saw because of trying what I just wrote your on your own. You mileage may vary.
Gordon