James, I still don't believe in putting the router in a box, even if it is well ventilated. The box will not provide as good a dust collection as a pickup very close to the router will. Any box will have dead air spaces in them usually in the corners. Even if you drilled a hole in every corner you would just move the dead air spaces to the center of the panels. Whenever you have live air moving past dead air you are going to get turbulence. That will cause heavier particles to drop out of the air stream just as they do in a cyclone. Because the vacuum port is so far away from the cutter you are depending on all the particles to stay suspended until they reach the vac opening, which is unlikely to happen.
The best under table arrangement I can visualize would be a half moon shaped vac chute on one side of the router and the other side totally open. The vac would cause a low pressure area at the bit and air would rush in from every direction to fill the void. The only particles that would escape would be the ones that get thrown at "escape velocity" in the opposite direction.
As already pointed out, an under table pickup will mostly pickup dust from routing operations on the edge or below it. Since we operate above the table, that is where I want to catch dust, the stuff that would otherwise wind up in my eyes and lungs.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.