gas mileage Mechanical vs Vacuum Secondaries

I really like lxguy's response as it is close to what I plan. I have a 750 holley vac sec with a proform carb body, a box stock 650 dp, and a thermoquad that I will be trying. I like to think of it as a carb for all seasons. I know this may seem excessive but all the carbs were used and picked up very reasonably. Actually I have as much in all three carbs as what the 650 dp would cost brand new.