What about chambering it in 338 RUM? It will be a bit more forgiving in the mag box department. It's about .08" shorter.
I've also heard that the new centerfeed actions are easier to build RUM length cartridges with a few mag box modifications.
I think it was Earl Fouraker here, that just built a nice 7mm RUM on a new centerfeed action.
Here it is.
New long Range Savage 7Ultra