Adjusting heart rate zone to account for POTS elevated heart rates

A friend of mine has POTS (Postural Orthostatic Tachycardia Syndrome, a heart condition that causes the heart to beat faster than a normal heart would during exercise. Her maximum displayed heart rate is 206. Yes really.).

As a result her workouts often show that she's done an anaerobic workout when she has really only exerted a moderate amount of effort.

In order to get her workout scores to be more in line with her level of effort, rather than her heart rate, I thought we could reset her heart rate zones so that they were more skewed toward the top of her range. Does anyone have any experience doing this? If yes, what heart rate ranges did you find worked with the different zones? Thanks in advance for any insights you might be able to provide.