Thanks, [MENTION=146168]Garthr[/MENTION]! Your description and associated link is the first time I've ever seen an easy to understand description of this process. It really helps to know how deep to thread the two equal length spokes into each nipple: just to the top of the flat head slot (not to the very top of the nipple). And it also helps to use a digital caliper between the two j-bends.

I came up with 612, close enough to make me feel comfortable to use the published 613.

Learn something new every day!