Thank you RAPCOM, I was in the odd position where I lack the means to determine the PA angle with any certainty from an existing gear while being able to make one once knew! Begorrah!
You never know I might even get the 'ol Comet out on the road again after something like a 20 year layoff, we've been together 40 odd years man & boy, (please feel free to hum along with the tune). (Excuse: Marriage, mortgage, kids, you get the picture!)