AI Waypoint - Take into account unit Size/Radius?

Hello,

I'm messing around with different path finders/waypoints/navigation systems for my game. The ones I've used so far don't actually seem to take into account my units size/radius.

So if there is a small gap a human can walk through, it will assume that a tank can drive through this 'small' gap too!

I've also played around with the UnityPro navigation system. However, there is a radius option for each individual unit that is using the nav agent. But it doesn't seem to actually do any difference at all! I've made a very small gap between 2 cubes. My human has the correct size radius and successfully walks through the gap. My tank, however clearly will not fit through the gap, and the radius shows that. But when played - the tank drives straight through the gap. I'm under the impression that the nav system for UnityPro is still in its betas, correct?

If so, I shall ignore that. So - my question is; does anyone know of any pathfinding AI that takes into account the units individual size/radius? My game is built around a grid system, so a grid pathfinding system is fine.

Thanks.