I made one for my shop that is very similar. I use a Mitutoyo dial caliper to take measurements before coaxing the hanger back into alignment, then check with a long straight edge between cogs for a final eyeball of alignment. I easily get less than the 4mm rim deviation at the rim as recommended by Shimano for alignment. Works well but no doubt slower than a DAG-2.2, but I am retired so no worries.