My old Jones underlever hammer gun (1875-1880ish by the proofs) is a clown car compared with a modern double. With non-rebounding hammers, you must go to half-cock to open it. Closing the action requires coordination as the barrels come down so the lever meshes with the underlugs.

I would want to spend some time doing drills with it to overcome the awkwardness, but for dangerous game its not a good choice unless in a world where the alternative were single-shot rifles, like when it was made.