As the best performance for a normaly asperated piston engine is between 6 & 8000 Ft That is normaly were you will find me and a bit higher if I can find a good tailwind.
The policy works quite well, once did Glasgow to Booker in a PA28-161 in 2 hours 06 Min, most of the flight was at FL105 and you have guessed it a very big tailwind. ( the B757 took 1h 15 to go LHR - GLA to get me up north to pick up the aircraft !)
Oh work its FL410.