This is delicious but we think that Montenegro is the wrong Amaro for it...too timid up against the dark Rum. We go with Nardini, which makes it much more expressive...but we drop its volume down to 25ml.
Yes, Punt e Mes is too much for us. We do this with Cardamaro. If that's altogether too mellow to your taste, then add a dash or two of your favourite bitters...we go with Angostura Orange.