I made a 3-gallon batch of this, and it's fermenting at Day 6 right now. A couple of learnings so far:
1) Didn't want to spring for Alexander's Muscat concentrate, so I looked for a grocery stores equivalent. Ta-da: Welch's White Grape Juice concentrate, available in some stores (got mine in Safeway). White, not purple, because of the color. We'll see how it turns out. It may be a bit more "grape"-y than using muscat concentrate, and if does turn out grape-o-rama-riffic, perhaps scale back next time.
2) Added the grape juice concentrate on Day 5. This made the krausen go crazy. Like, the 3-gallon batch in a 5-gallon bucket is touching the lid today (Day 6). So, be prepared for that to happen maybe. I'm using US-05 BTW.
3) Didn't add saffron. The recipe's small amount won't affect the taste one way or another. And the beer is already yellow, so ... meh. Although if we're futzing with the recipe anyway, and want the beer to be yellow-yellow instead of beer-tan-yellow, some may wish to consider turmeric as a cheaper alternative, if you already have some lying around from Indian cooking, for example. Warning, though: it does have a more assertive flavor than saffron. Sort of mustard-rutabaga-ish. Since I already altered the grape juice component, I didn't screw with adding turmeric here. Too many variables.
We'll see how it turns out.