From what I understand, the Royalist sentiment was strongest in the south of Italy, just as the north was a center of Communist sentiment. I agree that VE had abdicated after he got rid of Mussolini and given the reigns to Umberto they may have more support. I think the best way is if Italy attempts to become a neutral power under Umberto who will passively allow the Allies to use their territory while laying down arms and keeping the Italians in the south not only alive but loyal to the government. With a real support they have a far better chance of survival. But to be honest the goal is to make themselves relevant to the post Fascist Italy.