Vacuum advance tuning to maximize cruise MPG?

Ended up with 24*/38*/56* full manifold vacuum, 14" vacuum full canister travel 22*
No detonation, 16" vacuum at 2600RPM/70MPH
One thing I noticed is engine braking is less when you decelerate; which is a good thing from everything I've read.
I need to go on a long cruise this weekend and see if the MPG gets better.