That is a spiffy layout. The template would be idiot proof. At work we figure arc length on the outside diameter. Knowing that 8 holes evenly spaced in a circle will fall at 45° to each other, and working (for example) with a 24" diameter circle, each degree will equal .209". 45° will equal 9.42" measured on the outside diameter. Starting anywhere, we layout 7 locations at 9.42" apart. Then we snap a line from the center point of the circle to each of the 8 marks on the outside diameter. I like your idea better.
The engineers I work with have that information on the computer, it just never makes it into a template. The bad part is the young guys on the shop floor don't know there are 360 degrees in a circle and don't know what those little lines on a tape measure are.