Needs a sweet (rather than herbal) vermouth and a "spicy" (rather than smooth) bourbon to offset the bitter taste of the Campari. The first one I made (with carpano antica & Makers 46) was overpowered by the Campari. I couldn't taste the bourbon at all.
1 1/2 bourbon (Buffalo Trace)
3/4 sweet vermouth (Punt a Mes)
2 dashes grapefruit bitters
Combine ingredients in mixing glass with ice. Stir. Twist lemon peel, coat rim & drop in