Personally, I'd do a 7 Dakota
, or a 7/300 Dakota for a big 7. Barrel life in the RUM and STW are too short for me.
The short barrel life of the real overbore cartridges is only part of the issue. For starters, they tend to be challenging to tune loads for. Once you do establish a good load the throats are firecracking and eroding way too fast. This means you're constantly tweaking BC's, powder charge, and seating depth to keep your loads shootin' tight. It get's aggravating...
I'll take easy tuneability and consistent accuracy over raw horsepower most of the time. Sometimes..... ya just got to burn some powder! When speed scratches your itch, I'll take the RUM over the STW.