Aerobatic weight limit is 1375lb and typical empty weight for one with O320 and FP wood prop is about 950-1020lb. So with 2 180lb people you can only take 30-40lbs of fuel and you could well have the CG aft of the aerobatic limit.
Plenty of people do aeros 2-up in the RV-4 and that is quite legal under FAA experimental conditions, but not under LAA limitations unless you build very light and most of the weight saving opportunities push the CG further aft.
The consequence of the aft CG is very light pitch forces making it easy to exceed g limits at high speed.