Yup. See my recipe in the recipe dropdown near my pitcure, for "Gingembre et Pamplemousse Quatre".
I just sampled the beer again the other night and it's amazing. Been in the bottle for four months and the aroma is this complex mix of ginger, grapefruit, honey and fruity/spicy notes. Munich malt comes though nice. Hugely complex beer.
Used 30 grams of very fresh grapefruit zest. Use only the color part, don't grate into the white (bitter) part. For me, 5 medium sized grapefruit were enough. The grapefruit character really comes through. You can use one of those little graters that are used for nutmeg.