It's either tail heavy or waaaay out of trim and the pilot over controlled in my opinion. I rarely trust the CG recommendations on ARF's as they are wrong as often as not. On warbird types I like to start out at around 28% of the total wing area and adjust from there. I also always dial in a bit of down elevator on a first test flight to keep the airplane from lifting off before obtaining flying speed. Last, but not least, I like to start with all control throws set to moderate throws on low rate with high rates set in case they are needed once airborne. I've seen too many airplanes wrecked on test flights because the control surface deflections were set to rediculous amounts and the pilot over controlled in an out of trim situation. Very often it appears exactly like an aft CG situation with the airplane all over the sky!