Sorry for jumping in - and maybe I missed some discussion about this elsewhere; but I didn't see any mention above about the height of the HH, which obviously changes the width for a given length of pipe.
Here's a link to a calculator that might be helpful:
https://www.handymath.com/cgi-...
That's quite a project you have going, Nakoma - I can't wait to see photos of your progress!
(edited to correct link to arc calculator)
