You can find your neutral point by using some math. It takes the tail volume coefficient and compares that to your wing chord. I'd have to look up the forumulas.

But an old cheap and dirty way to figure it out is to cut out a top view of your airplane from card stock. Then balance it so it sit's level for and aft when balanced. That point is roughly your neutral point. From there your center of gravity should be about 10% of the wing chord ahead.

In your case your MAC is pretty much 11 inches. It'll be a trifle less thanks to the wing tip shape but you can pretty much ignore that. MAC is mostly just a fancy way to say "average chord size and location".

For your Eindecker the wing shift will have only a small effect on changing the CG location. If you put the new CG as far behind the wing's leading edge as it was on the original model it'll be fine. On the other hand if you meant to leave the CG at the same spot back from the model's nose then it won't work. The CG MUST always be located as a distance back from the wing's leading edge. (basic I know but in case you didn't know)