RE: New Patriot XL
it really depends on the engine. non performance engines i break in with the prop I'm gonna fly with, i find peak and then back off enough to keep it cool and lubed, the only cooling down it gets is the time i take refilling the tank. on performance engines (like the Jett) i use the prop i plan to fly with and as soon as it peaks, back out a good turn or two to wet everything and cool it back down some (keeping track of the RPM) and then kill it and allow it to completely cool. i then fire it back up with a prop 1" in diameter smaller but the same pitch and i run it at WOT leaned to the RPM i got off my flying prop, it'll still be a pretty rich setting but it breaks in the engine at the RPM i intend to fly at.
kc
EDIT: this does not apply to gasser engines, they have a break in all of their own.