<b What a drink! Just two ingredients, but they mix well and make a satisfying drink. I polished off my bottle of Booker's with this recipe, but it was worth it. Some might like a sweeter vermouth other than Punt e Mes, which will be a matter of taste, just as some might like a different overproof bourbon.
Regardless, changing overproof bourbon brands and using a different sweet vermouth will probably still result in a cocktail that will satisfy most bourbon lovers. By the way, I added two drops of Fee's Whiskey Barrel-Aged Bitters, with a pleasant improvement. Others may prefer a different bitter; experimentation is the key. I rated the Moto Guzzi between 3.5-4.0.