Can you put an overcharge Valve on a dueling Pistol? It only has 1 shot already.

Up to your gm, but I'd lean toward no.

The overcharge valve says it dumps the power pack to generate a massive shot and can work with any weapon it could logically work with. The dueling pistol specifically states its power pack is only good for one shot, and it already has huge damage. So I'd say no simply because the dueling pistol already fires overcharged shots naturally.

Yeah, this combination would fall under "stinky cheese" for me, for pretty much the reasons that Ghostofman cited.