Great suggestion. Yes Benedictine's always good in everything I've tried it with. Have you tried Boomsma Claerkampster Cloosterbitter? It's a stand up substitute for the Chartreuse if you can get it.
No, we haven't tried the Boomsma but notice that it is available here downunder. It seems to us that one of the problems with all potential substitutes is that none of them get anywhere near the ABV of Green Chartreuse and that this has inevitable consequences for flavour comparisons.
Indeed so true of all the substitutes! I'm looking at my three quarters full bottle of Verte and finding ways to stretch it. If a cocktail calls for 5ml Chartreuse the Cloosterbitter may not cut it. Not bad in a Last Word and cost effective as well. Closest match imho. Cheers