Nope, you have the correct concept. But I would first make sure the spacing on the drive side is correct as far as chainline goes, then I would just fill in on the non-drive side to get it to 135mm. I would just go to a hardware store and get a bunch of washers. Won't be pretty, but it will be functional.
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Il faut de l'audace, encore de l'audace, toujours de l'audace
1980 3Rensho-- 1975 Raleigh Sprite 3spd
1990s Raleigh M20 MTB--2007 Windsor Hour (track)
1988 Ducati 750 F1