You may have signed up to the wrong site, Justin, if you are looking for more powerful loads to shoot through older doubles. Most of us here go to some extremes to create and share loads that are just the opposite. Old guns are old guns, and generally should be used only with loads that purposely are created to be lower pressure than the gun's original proofs, in the interest ggenerally of helping some of the really fine old guns make it another two or three generations. Could you tell us what guns you want to use, and for what purposes? That's a beginning point for us to know how to better answer your question. There are no doubt other sites better suited to sharing magnum water fowl type loads, if that is the direction you might seek. Some here no doubt go both ways (I always wondered about a couple guys in particular that might go both ways)
If you have a modern thunder stick, that's a different story, and some here can answer better than I for such guns. Proof levels can be determined in some cases, but you certainly don't want to approach proof load levels in any gun, including modern guns. If they don't blow, they surely will wear very quickly.
