So far, a 75mm Sprgr 39 for the KwK 42 cannon in the Panther tank as eluded my grasp. My plan is to convert a standard 39 into a 39/42 model by adding a driving band. May I request side by side comparison drawings of the two projectiles? I assume the two models have the same overall length and location of the lower driving band? Will this idea work? I have several spare projectiles for this project.