Eric, I have not logged in here in awhile, hence my late reply. I am not a CR “expert,” so take what I say with a grain of salt. I’m just a guy who has had a lot of experience with running in general, and CR in particular.
I agree with you that there is an optimal pace for most of us, although it can vary quite a bit, depending on one’s age, gender, and fitness level, among other things. Going too slowly can indeed make running more difficult, as you note, since one is getting less energy return with each stride, and probably using different muscles than usual.
Similarly, we each have an optimum stride rate. I would disagree with those who recommend that we all strive for 180 strides per minute. As you have found, at some paces that’s too slow; at other paces, it’s not fast enough. At slower paces, instead of thinking of my stride as slow and short, I prefer to think of it as “light and quick.” At the faster paces of workouts and races, 180 spm is often too slow. The cadences of elite athletes confirms this.
As an aside, I find in the infrequent instances that I run with a metronome, I tend to go faster than usual with less effort. It seems that my stride smooths out and lengthens as I focus on the steady beat of the metronome.
Good luck to you.