Missed the gravity pretty badly(had my water losses WAY off on the new system) on the first batch of Blonde on Blonde in the basement system, so I bumped it up with a pound of Muntons Extra Light to get the gravity in the ballpark. Wound up with a 4.8 abv cream ale that's dangerously crushable. Experimented by substituting Sterling for Kazbeck, definitely a workable substitution.