I'm getting ready to mount the engine but I'm confused. The manual says 3 3/4 from the bottom with the lower hatch off, Model airplane news article says 3 1/4, and Rc modeler says 3 1/2. The 3 1/2 mark seems to be the best from what I can tell.

Anyone experience this problem? Motor is going to be Irvine 150 with a hanger 9 metal motor mount. Thanks!