don't forget the placard thats in the 47 about manifold pressures for 200 hp at various temps and altitudes...that technically becomes your limiting factor. since your transmission is rated for 200 hp of input hp, if you pull 25" MP at 5000' you'll actually be using more than 200 hp from the engine (you're into the 65 hp of spare power for which the engine was de-rated in the first place). i've never heard of anyone worrying too much about that MP placard, especially since the 200 hp limit is not actually stated as a limitation in any of the FM's that i've read.