Based on Beuchert's "BITTER BOURBON GIUSSEPE," which advertised "cymar, bourbon, vermut negre, orange bitters, lemon juice":

3 parts Rye
2 parts sweet vermouth
1+ parts lemon juice (to taste)
¾ part aperol
¼ part St. Germain

Orange bitters.
Angostura bitters.

Shake well with ice, strain into a coupe or whiskey glass.