As far as Last Word riffs go, this is probably my favourite. Used ~7,5 - 10 ml of Lagavulin 16 and it introduced subtle peaty/smokey hints that went well with Chartreuse.
My preferred variation is with equal parts maraschino and green chartreuse - 15 ml each - with a Lagavulin rinse in addition to the 5 ml in the cocktail. I feel the flavours better balanced that way, and the hint of smoke and peat comes through without getting lost.
To my taste, 10 ml of the Maraschino and 15 ml of the Chartreuse was a step in the right direction. 7.5 ml of Laphroaig (added 2.5 ml more after the shake/strain) helped to amplify the smoky edge just enough. But in regards to the notes and modifications, yes, a mere rinse with the Islay is not nearly enough.
I'm not sure if it's because I used yellow Chartreuse, but the Maraschino was way too forward in this to me, to the point where I wasn't getting much character from the Chartreuse, not to mention little if any Islay smoke. The ingredient mix sounds interesting. I guess I'll have to play with the specs.
I think either one isn't enough on their own, but I think both of them together - a rinse of the glass and 5 ml in the shaker - is perfect. It's still subtle - just a hint of peat and smoke - but keeps it from getting lost in the other strong flavours.