For whatever it's worth, I've noticed that the difference between a scratch player and a 5 HCP is just over 7 strokes (both here and here). The difference between a scratch player and a 10 HCP is just over 12 strokes (here).
I think I did the math right from those charts- adding and subtracting positive/negative gains and losses can mess with my head.
I got into a ball striking slump. I couldn't get my clubhead squared at impact. It turns out I was bowing my wrist at the top a bit too much. It took a few camera shots to identify the regression. I fixed it but my HI is trending at high 15s. I need to have a few good rounds to keep my next HI under bogey golf land.