Well. Its easy to write hammerguns have worked before for dangerous game..why not now?.
Back in the ol`days hammerguns were the norm and most used as nothing else were available. That meant sportsmen in general was proficient with side-by-side hammerguns way more than we I used to here in 2020.
I haven`t any experience in hunting dangerous game and I doubt I will ever get it. This however I can recommend if one wants to gain experience in using a side-by-side hammergun is to buy a hammer shotgun and go birdhunting in SA, England or other places where one can enjoy mass shooting and develop gun practice. I am sure after a week cocking hammers and learn point-ability the adaption of this empirial gained knowledge to a big game hammerrifle rifle wouldn`t take long. It all about workability with use of hammerguns. The Jones underlever is a bit slower to work than a toplever for volumes of fast flying doves but fast enough. I am not in a hurry.