I had one with a .46 Irvine and ran into the same problem. I added some weight on the tail skid. At 4,500 ft. the extra weight was still not a problem. I used a 12.25 x 3.75 prop and had power to pull straight up out of hovers.

I would also urge you to balance the plane right at the cg or behind it. When nose heavy, these things suck while inverted.

You will love the plane. Gotta be the best $100 arf out there.