I, too would change the mount. Dave Brown makes a nice one that works well with the 4-Star.

I think your problem is not all engine mount, though. You stated it "balanced ever so slightly nose heavy" but was "very, very nose heavy" for the maiden. I think either your tailplane incidence is off, you have too much up thrust, or the balance is way, way off, if you put in all the available trim and it still flies nose down. I see guys at the field with .90's on their .40 size without having balance problems. I have that DuBro mount on one of my planes, works great for vibration, but it does stick the engine out there, especially a four stroke.