Dave,

Using a picture form the manufacturer's website, I have re-calculated the CG at 25% of MAC.

I did it graphically at scale, resulting in 4-7/8" measured aft from the point where the leading edge of the half-wing intercepts the side of the fuselage.

That is a conservative location and a safe point to start testing a more aft location in little increments (1/8" at a time), until you feel the airplane as responsive as you like it.
Once the elevator becomes twitchy, it is time to return one step back and leave it there.

If you verify that your MX2 balances approximately at 4-7/8", you should find the problem somewhere else (mix or thrust angle).

Another idea, if everything else fails:
Verify that the thrust angle doesn't change when throttle is fed.
That could happen if there is any problem with the structure or engine anchoring.

Again, best luck!