Manifold pressure at different altitude

The engine is not afraid of heights!  All that matters is the RPM and the MAP.

Section 5 of the Operators manual shows that you can go WOT at 5500 and above, and anything goes as long as the MAP is below 26"

Meaning that once you are above ~5000 ft., the skies the limit. 

You could COARSE Up (Down) to 4000 rpm and WOT and still never be able to make much over 25".

From the Manual...  5000rpm and 27.2" will produce 75% power.

You could set the prop for 5000rpm and set the throttle to anything that keeps the MAP below 27.2.

This would be doable at Sea level, but might not be possible even at WOT above 3000 ASL.

Check out THIS thread.