Hey all,
I just added this to my Bench Dog Cast Iron Router table extension:
http://www.general.ca/accessories/ac.../a_40-130.html
It required some modifying but it turned out quite well (IMO of course). Firstly, I needed to exchange the dust outlet position with the air vent position because there was not enough clearance between the router table extension and the body of my table saw. All that required was grinding the rivets off of the air vent, drilling new holes and re-riveting it to the rear. Then, I removed the dust outlet attachment and, instead of dealing with the odd shape (the existing air vent hole was square and the dust outlet attachment was round) I purchased a $5 outlet from the local woodworking store and riveted it to the router enclosure. As you can see, it worked out quite well. I could have used the original dust outlet attachment, but it would have required sealing the corners which were very slightly exposed.
After that was taken care of, I took two pieces of angle iron and mounted them into the two front and two rear existing holes on the underside of the cast iron Bench Dog router table extension. This actually lines up perfectly and, because the angle iron I used had holes already in it, I found holes that lined up and it installed quite easily!
Once it was mounted to my router table, I sealed where it attached to the table saw extension with silicone. Also, for that matter, I sealed the bottom plate of the router table extension with silicone as well as the dust outlet attachment to ensure a bit more of a seal from those locations (this way the majority of air being pulled into the enclosure will be from just the bit location and the air vent itself).
Now, I still wanted to use the fence hangers so, I ended up bending the angle iron slightly to accommodate the fence. I could have simply used heavier gauge steel instead of angle iron but I didn't have any handy, which is why I just bent a portion of it out of the way.
Anyway, I really like this enclosure. It appears to be of great quality and the modification was pretty easy to do and it was mounted very solidly!
Enjoy the pictures. Hopefully they help someone who is looking at doing a similar set up.