+1
I've played with all sorts of setups, including ball heads, leveling bases, etc, and the Arca setup with leveling base is the best I've found for pure stability. But the cradle/leveling base is very good too and is more adaptable. I do the same as aalf with regards to tensioning the base so that the rifle will stay in place but can still be moved without excessive effort. The only other thing I would add is that I use my support hand to pull the base/cradle in towards me with the rifle mounted on top, as that tends to dampen any vibrations or instability that come from an imperfect position.
