I think I have finally gotten to where I have a loose arm every time on my strokes. What a difference. I played next to some college players last night and noticed - these guys and girls don't all hit insanely hard, but they have that big huge clean contact sound over and over. It comes from that loose arm and torso twist. Once I got it going, the ball contact was sounding huge and the pace was heavier.
Finally got to where I do as well a lot more often. Effortless power now. Getting it going on serve too, which is also an eye opener.