Brunner, welcome to the forum, like yourself I’m new here after becoming disillusioned with another site. As far as your HR theory, it’s been a while since I studied the HR subject in detail but you bring up an interesting point. After an injury I’m slowly re-building my level of running/fitness and not using a HRM. I’m not even using a watch either, just base building and fartlek right now.
I may get another HRM down the road, but never run your pace. I’m 47 and just trying to run a 3:35 for Boston in 2007. MikE