Bruce,
I think (and that's dangerous) if you go strictly by the numbers, to match the length of a 1xl nymph hook with a 2xs scud hook, you'd have to upsize by 3, which seems crazy to me; I just go up by 1 and things seem to work out okay. Not sure if the Dai Riki's are true to size or what "true" really is; seems to me this is as sketchy as thread size with the whole ought vs denier difference. Anyway, just my 1/50th of a dollar.
Regards,
Scott