broken grips

[OH Osthaus]

i would expect the grip design would not be a contributing factor

the layout of the grain

the presence or lack of oil soaking

and any previous abuse that might go unnoticed

I would avoid any narrow wrist or smaller frames

I'd have the stock examined and reinforced - a staple added and some bedding

[edgarspencer]

I think you would find a straight stocked double rifle a bit awkward. I think an 0 frame would handle the recoil of a .405 with ease, especially if you're handloading. My dad had a 00 framed 28 that started life as a VH, and was beautifully engraved by John Warren, with a second set of barrels made by Joe Jurjevic, in 38-55. It was made for Ed Spicer, who was known for commissioning some awesome projects. Dad traded it back to Gary Herman for something a bit more traditional, and Gary sawed the pistol grip off and made it a straight stock. He admitted afterward he hadn't thought it through, and as a rifle, it was very unattractive.
I've had a couple .405WCF doubles, one a German box lock, and it wasn't beefed up. Kynoch loaded .405 but they were too hot for a '95 Winchester.