@aarestor is correct and that will tell you if your up / down thrust is off. If you go full throttle with the plane trimmed and cut the throttle and the plane still flies level, then you are tail heavy.
I know I may get flamed here but we'll see. On a fully symmetrical wing like your plane and nearly all aerobatic planes the wings DO NOT generate lift. Angle of attach makes the plane fly along with modern power levels pulling the plane along.
So to check your CG (after you check for possible thrust issue) you need to fly straight and level at about half throttle. Roll inverted and see how the plane acts then. When you do this at a 45 degree up-line depending on the amount of power you have you have angle of attack and the wings are lifting the plane and you will get a false indication of CG. This is especially the case when you are very close to neutral as you mentioned.
I will tell you that I have a Great Planes Cap 580 that was brand new and I just built it recently. I much prefer that plane just a tad more on the nose heavy side than neutral like I fly my other planes. It does just about everything better not being neutral and draws perfect scale lines.