Well I see that the Sticky has been updated but it's still a bit misleading. I don't think that you should recommend soaking copper blocks or brass radiators in vinegar at all. As for radiators, why substitute vinegar (95% water) for isopropyl alcohol (organic solvent) if the flux is water soluble? I'd like to see how much 'gunk' alcohol removes after numerous flushes with warm water though. Perhaps you could change the cleaning recipe to just numerous flushes with warm/distilled water then possibly flush with alcohol (if it turns out this is necessary).