In the event you have to drill holes for mounting there are a few methods you can use to mount the engine with. You could use the device that great planes sales, for finding the holes, not sure whats its called. There are different other tricks you can use as well. The method I use is a click pencil I stick in down inside the holes mark my holes then use a center punch being careful to hit the very center of the hole then I use a drill and tap to thread the holes. Where you place the engine on the mount could effect your CG (center of Gravity) but its better to have a nose heavy plane rather then a tail heavy so you might want to mount it with in around 1/4 - 1/2 inch of the very front of the mount.

Randy