Hi Doug,
I have a number of posts on this thread. I address the ducting in post 1458. I recommend starting at post 1454 though. Hope it helps. I really like my Revo engine.
Oh man, I just realized that you were the one I responded to in the original thread. All I can say is, trust me on this. Forget the shroud and fan. Use the ducting. I have flown the plane this year at Muncie for the Indiana Warbird Campaign event. This was the hottest day I have ever been to an event. It was crazy hot. 98 degrees and very high humidity. I know 98 degrees may not seem that bad since you are from Texas, but the humidity kills us here. And there was very little wind. I flew about five or six times on Satureday. And the engine ran fine. You could tell the air was thin because the power was down. And it was so hot the black top runway even gave us fits because the air rising off of it. You can see in the attached video from Youtube that when you can in to land, that when the plane would get to the black top, it would literally balloon a bit. It sure gave me fits. Also this was my first time taking off and landing on blacktop with the P-51. Definately more work than grass. I struggled a bit.
http://www.youtube.com/watch?v=0Z2hgiar9sA
I start at the 3:09 minute mark
http://www.youtube.com/watch?v=dpUwg...eature=related
Hope you like
Karl