I initially used a precision 6" scale with clearly marked mm graduations to set the float height to 17mm, but because you can only hold the scale so close to the end of the float, it's sort of hard to hold the scale and the carbs in the correct attitude and accurately read the height of the floats.
So that’s when I decided to machine up a custom float height setting gauge out of 3/16" thick aluminum which makes it very easy while holding the carbs in the correct attitude to accurately check that the float height is set at 17mm, and it's simply held against the float bowl surface on the carb body over the float.
When checking the float height with my setting gauge that I had initially set using my precision scale, I found all four floats were off by 1mm+.
I've made float setting gauges like this before for other bikes I've owned, and it will be interesting to see how setting the floats using this gauge this compares to the liquid level float check procedure.