Thanks for the left/right correction.

ERD as measured by myself including an estimated 3mm base in the rim. It's for an 18" wheel. It was originally 1x lacing and it's a reputable brand (R&M), so I guess I'll do the same.

"I see the DT calculator does not give warnings for things like improper flange distance. the one I use does.": What's the site?

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Edit: Is this a better/more reliable way to check the offset?