Just measuring these out based on the HRC manual and I just want to double check that the patten isn't regular. Looking at this page:
http://akhara.com/nc30/nc30hrccarb/index.html
and also at Cammo's carbs in his carb guide, all the holes seem regularly spaced, however, the diagram seems to have a larger offset on one side of the centre line to the other:

I'm reading these as 18mm and 8mm respectively. I guess the ultimate questuon is... does it matter?
Cheers
Luke