RE: Excelleron 90
I am running an inverted OS 120 in mine. But... a high fuel tank is NOT GOOD for a couple of reasons. One is the expected problem with mid-range transition. Frankly, I do not notice the CG change with the provided tank position, but then again, I don't notice a lot of things. If you move the tank back, you might consider using a smaller feed tank in the normal tank position.
John