The TroyBuilt version has reduced the dihedral of the main wing (to reduce roll coupling in a knife edge) and done a few other "tweaks" in their opinion to make this warbird fly a bit more predictably and with IMAC like performance...Personally, I think a model of a warbird should look and fly in a similar way to the original.....I'm not really interested in hovering, lumpshevaking, (sp?) or doing other 3dish or IMAC type things that the "tweaks were meant to add.
I'm adding the same 5 cylinder you are speaking of (ASP400) the 80" CMP zero and it will fit there with more than enough power to fly it very well. It will probably fly the 90" in a similar way if not more scale.
Here's a video of a few engine runs I did on the bench last fall..very good power and very good runtime on just a 16 oz tank....I'll probably go with a 20oz for flight though.
http://www.youtube.com/watch?v=LK1jF...8&feature=plcp