If you are modifying the engine mount, for a gasser, I woulden't get too carried away, an inch or so is plenty. If you are using the stock engine box, you had better re-glue all of the joints. The three I have inspected have been awful, and just fell apart. But that is easy enough to fix with some triangle stock and epoxy.

Where is everyone ballancing this plane, 3-3.5in aft from the leading edge of the tip??? or more??