Google turns up lot of recipes for wine from fresh grapefruit, seem to use zest from one and juice from 6 per gallon (possibly US gallon). Dunno what you'd do about the missing zest with tinned. I expect Google would turn up a recipe for tinned if pushed a bit harder, but as _you're_ the one with the grapefruit...
Don't recall seeing any grapefruit recipes on this forum, but then I don't like them so I may have skipped past without thinking about it