Like some journalists I've met, this cocktail is classically bitter and sour. Hence, I balanced with an optional splash of sugar syrup, which I've increased...
It has been a year since last drinking this cocktail at which time I upped the gin to 2 oz as per Difford's 15th edition recipe. This year I went back to the above recipe and having tried this twice with 1.5oz of gin, I can report that for me 2 oz is the way to go.