I know they made small shank RUM's cuz I own several but I have never seen a small shank WSM.

I remember SSS saying some years ago that a small shank RUM was "98%" on the safety margin per Savage's tests which was why they went large shank.
(He also said that 98% was a safe setup, not trying to imply that the RUM on a small shank is not safe, as I shoot them all the time)

The WSM being even larger would be pushing the envelope even further would it not?