I've had a pair on permanently since at least April '18, maybe a little earlier. I like them, no problem, reassuring really & useful, you see fuel problems early. They're on a pair of 32's, but you have to use the new clips as the wire used changed over the years, I thought they'd crack under some of the tension I put them under on different bikes. They didn't, just flexed a bit & went back to shape, so beware of this if you use them to check other bikes. I just hold them up with my hands to get a reading now on other bikes.
The scale on the side is a guide to 'equality', different bike ranges sit on their stands differently so a set level is meaningless. I set mine 14mm below the gasket edge of the bowl, filled and off the bike first. I now know what to look for on my bike now from the scale. It's worked for me for years on that figure.
To make them handed you just have to unscrew the appropriate slug, there's a metering hole going through to the main chamber from the 'well', a little like the old float bowls. I get a 'differential' choke so it seems to work as normal.