The BEST way to use teh RPG is from a 3rd story window shooting down onto the engine deck of a tank, preferrably after passing so it will not shoot at you. For redundancies sake, better to have many people shoot at tanks from many directions. And it will take mulitple hits to knock the tank out either because you will only "wound" it, or you may not hit it in a critical area...ie, a shot may go through the fender or some such.
The idea is that you have a +50% chance to hit a tank sized moving object at 200M. It does not mean accurately. The PRG is best seen as a area effect weapon (on the tank) rather than a sniping effect weapon. Too much Hollywood and video game effects gives the wrong impresson on what weapons often do, especially small ones. Nukes they usually do correctly.