That is going to depend upon the weight of the pistons etc. It looks to me from the photograph that someone has already put the extra holes that I have found necessary into the flywheels near to the crank pin but I do not start off with the extra weight needed. I weight the small ends of the conrods, the total weight of the pistons, ring, gudgeon pins and circlips. Calculate 46% of that. Subtract the weight of the small ends and then work out what is needed to balance the flywheels. For racing some people prefer 50% balance factor.