I used a single Suunto compass with adjustable tacking bands for many years, and then switched to 2 for reasons below. I found it worked great on flat water, but to confusing in the ocean. Basically, the tacking angle on flat water was 90 degrees, and in the ocean it was 110 degrees on a TheMightyHobie18.

It was confusing in the ocean because the waves would not come from the same direction on the race course as the wind. The waves continually changed their height, angle and spacing to the boat throughout the day, making one tack's VMG appear better than the other tack, change. The sea state/angle changes during the race, the tacking angle can be 50 degrees off the nose on one tack, and 60 on the other, then as the waves build change to 50 and 65 equals 115 degrees.

Sea state/wave angle affects your tacking angle and VMG. On the race course in the ocean with no land bearing, when your compass shows a 5-10 degree change you need to know if this change is due to the wind OR sea state/wave angle, because when you tack your compass reading will be WAY OFF due to sea state and wave angle on the other tack. The sea state/wave angle can change with proximity to the shore. The wave
height and distance between waves can change due to depth of water which could vary
over the race course.

There were to many constantly changing variables involved adjusting the tacking angle in short course coastal racing trying to figure out why it changed from one tack to the other due to sea state/angle, OR did the wind change? A compass that can adjust the wind direction for each tack is needed to compensate for the sea state/angle, or two compasses would be more accurate. I'm not saying it can not be done, but it takes a lot of racing practice, when not to use the compass. Things are changing quickly, and keeping you eyes out of boat scored better.