In order for material cooperation to be licit, one must apply the same principles as for indirect voluntary. I believe that is the point of the Italian post. However, I am confused as to how double effect could be applied retroactively.
When I consult Prümmer's Handbook of Moral Theology, the four criteria he gives for licit indirect voluntary are: "1. the act is good in itself or at least indifferent; 2. its immediate effect is good; 3. the intention of the agent is good ; 4. the agent has a proportionately grave reason for acting."