Agent Size in Aron Granberg's A* Pathfinding Package

I've been using Aron Granberg's A* Pathfinding Package quite successfully. I was wondering if there was an easy way to handle agents of multiple sizes with this? Large agents end up cutting through walls and trying to move through gaps that are too small.

I have thought of using multiple meshes, but this is probably not ideal.

EDIT:

The solution I have come up with so far is to use the 'erosion' option with tags. I then set the characters' tag penalties based on their size. This does work, but is far from ideal, since an expensive path will still be calculated if there is no cheaper one. This means that the characters still overlap with the walls if their pathing decides that that's the only option.