MAC is not what you descrbied. It's the whole length of the average chord and the position that the average chord is located at. For non tapered and non swept wings the MAC the aifoil shape that is located at the middle of one panel.

What you described as being at the 25% mark is the neutral point of the airfoil, not the airplane but the airfoil itself. The actual ideal CG range of positions is determined by the wing, stabilizer and tail length all taken together to find the overall aircraft's neutral point and from that a % distance forward of that point to provide an amount of stability that is relative to the use of the airplane. Depending on the size of the tail the CG at the 3 inch point could easily be considered as fully stable enough or it may not be stable enough if the tail is short, stabilizer is small or a combo of both.