Actually the PH is Tony Sanchez Arino. The rifles he most liked for DG are the .416 Rigby and the .500 Jeffery. He also liked the .375 HH and the .300 HH.
He's got the right formula. Given the options available now I'd add premium bullets (both softs and solids as appropriate) and at least 0.3 sectional density. Meet those requirements, and you've got a great DGR. At least for my recoil tolerance I'm not inclined to exceed them by much - I doubt I'll ever go heavier than my 1886 shooting a 425gr Northfork solid at 2050 ft/s. That's enough (and all the gun can take).
