I don't think the ROTJ helmets were cast from the inside of the ANH helmets. If that were the case then we wouldn't have the much softer details on the ROTJ helmets because it would be closer to the actual ANH bucks. But if the ANH helmets were molded (from the outside) and then from the new bucks pulled the new vacuformed shells from these new (outside) molded bucks the details on the ROTJ helmets would start look softer. Just like if you took the ROTJ helmet (you just made) and made new (outside)mold from it, it would become even softer each time you made a new mold then buck. Because your not using your previous newer buck. Did that confuse? Yeah, i knew you couldn't use a vac shell to vac over.