LBS uses a DT published wall chart like page, to lay the rim onto, got their help since my Sutherlands data
is missing a lot of rims made since that edition was published.

I have a DT spoke ruler, you hook the spoke over the hole in it.
zero is the edge of that hole


I found some Pop-rivet washers in aluminum same hole size as the one in the rims

maybe a kludge there, for your spoke overlength situation..