Enemies of different widths? ex: Mice go in hole but cat knows he is too big?

I have a town with some wide and some narrow streets.
I want to add tanks and large enemies later but they will be too wide to chase smaller enemies in certain places.
Tanks to take a detour when they have to.

How?
Is it possible to have 2 overlapping grids but have the seeker or right component ignor one of them. So far it seems that they will use whichever grid seems good at the time.

Or another way?

Here you go :wink:

http://arongranberg.com/vanillaforums/discussion/1102/how-to-find-the-path-for-different-sized-units/p1

Thanks