Why fly a single engine over cloud covered mountains? You're safer following the valleys, provided you keep a few hundred feet below any cloud you see, as well as a few hundred feet above the terrain, and for your legal visibility take the distance at which you can see a low cloud against a grey background, not a white house on dark moorland.
I agree 100% with 172driver.
Loads of people get killed every year doing this. It requires expert local knowledge, very good aircraft handling (slow speed turns, etc), and appreciation of local weather conditions.
I have overflown the Alps and other bits, above an overcast. The only risk is an engine failure, but scud running in the valleys carries many more risks than that.