Kneeling or sitting (or that guy behind the tree), I get the hand on the mag; but not necessarily in those positions pictured as not most stable...
Prone doesnt really work IMO as to grip magwell, you're pretty far elevated above the ground, which negates one of the primary reasons for going prone...
That said, I realize the hot handguards do lead to magwell grips on the VZ58... To minimize that (mal)practice, here's my setup:
-NEA Handguards
-Magpul AFG2
-GoGun GasPedal, aluminum version