First, you have to be realistic. A piston airplane with turbocharging will have a true airspeed increase of from 1.6 to 2 knots per thousand feet of altitude above 6,000 to 8,000 feet where the natural engine can produce full cruise power. That is not much when you consider time to climb and, if flying with a headwind, the increase in wind with altitude. If your turbocharged airplane will do, say, 180 knots at 8,000 feet that means it will do 187 or so at 12,000 feet. That is an increase but it won't change your life.