If the mass of the fuselage is n and the force required to "accelerate" it at 1g is X, the force required to accelerate a fuselage with a mass of n/2 at 2g is also X. Of course the wings aren't massless, so reducing the fuselage mass by 1/2 would result in an acceleration of less than 2g, and reduce load on the wing spar even when the acceleration is taken into account.