Just made this with Glendalough Double Barrel, Cointreau, & Dolin Rouge and I really like it. I'm getting "barrel"/whiskey notes up front, then the lime and a subtle orange come in, finished up by the herbal notes from the vermouth. I've gone through 150+ recipes here so far and I think this is a Top 10 for me right now.
I started off thinking I had all the ingredients but I didn't. So I used dry Vermouth, maybe 1 oz (was making for 2) and ¼ oz of amaretto, ¼ oz of lime and lemon. Very smooth and very more-ish.
Many thanks for the feedback, Beth. I've added an explanation of the similarity between the two cocktails and a link above. I've also added a quote saying the same from Gary's book.