The spacers replace the instrument cups, cheaper than replacement nuts from CNW.
The basic functions (speed and revs) of the ACEWELL will work with positive earth, but not the switched functions, because the switches on the standard Norton (ignition, winkers, dip/main, etc) are in the negative line. The ACEWELL doesn't have a separate negative per function, some share a common negative, if you get my meaning?
I have a Rita ignition (two wires to swap) and a Boyer Power Box (again two wires to swap), took me an hour to change the polarity.
The readout is very clear large numbers and good contrast, I'm very pleased with the arrangement. Also allows better clutch cable routing.