The basic point is that no matter what you do, you can't fly slower than Vs.
The ground contact will always be made at a speed around that figure, at best.
I once read, from a famous aerobatic champion, that upon entry into IMC one could enter a flat spin and spin all the way down through the cloud. Presumably he would have intended to recover below the cloud... otherwise it's true his forward speed would have been low but what about the vertical speed? Maybe that is quite low as well - not something I want to try in the TB20
In general, the term "mountain flying" is intended to mean flying in the canyons. Often this is done with the tops shrouded in cloud. This is done a lot in the Alps, where you have huge valleys with flat bottoms, and often the cloudbase is thousands of feet above the bottoms. The pilots that do this are trained to know the area well, and to not enter valleys which are a tight dead end, etc.
I would not do any of that - I fly straight across the top at FL160-190.