Your thermostat, supposedly, is fully open at 192° F. An operating temperature of 200° is not unusual. Particularly in summer, the temp needle in my PV is invariably just a fraction below the red zone when idling. I have also noticed that the rear end of the head gets hotter than the front. Maybe that's because there is less air circulation there, or maybe the air that gets to circulate there is warmer than up-front. I have another theory that no one has supported so far, but which came to mind again yesterday when I put on a new Ehrling head gasket. While the two coolant circulation holes up-front match the holes in the gasket nicely, even though the holes in the engine are tear-shaped and the ones in the gasket are round, the holes in the rear are halfway obstructed by the gasket, so, I've been opening up the holes in the gasket there, and that seems to make a bit of difference - not a whole hell of a lot though. All that said, however, after worrying for three years about the temperature gauge and trying most of the stuff the others have mentioned here, I simply decided to ignore it till the radiator boiled over, which it hasn't done yet, and I have enjoyed another four years of happy, worry-free motoring. The others here are tired of hearing my stories about this, so I won't repeat them, even though, you would be a welcome new victim ;-), but I have twice over-heated two different B16s to the point where the red paint turned grayish brown, with no other apparent harm done than blown temp gauges.
And, yes, running on seems to happen most frequently when the engine is hot, but can usually be mitigated by changing the timing and/or the mixture a little. It doesn't take a big change, and in my experience at least, there is no knowing in which direction to make it - both, richer and leaner and more advanced and more retarded, have worked for me. It may for you, but then again, it may not, but what can you lose?
Bob S.