no pictures handy but that's actually the type of dsign the rules are trying to encourage now. notice that there are no restrictions on cage attachment points if they are part of the seat mounting - use this to your advantage as a cage mechanism AND a strong seat mount.

I still found it easier to bolt my seat in, as the tunnel in my car is very high and access to the side bolds is limitted. don't have photos handy but I attach the mounting brackets to the seat, then the assembly to the seat mounting frame. that frame or "cage extension" is made of 2x1 box tube, in a square laid on the floor and stitch welded to it, with legs up to the cage at the door bar and main hoop. the interior is attached to the tunnell with reinforcement plate simillar to a cage foot plate. holes are drilled from the top down for the bracket bolts, then enlarged from the bottom and a thin tube tack welded in to fill the hole. so I'm only bolting accross one wall of the tube which keeps the floor from having threaded protrusions all over it and the tube from being squished. I use allen head bolts from the bottom and nuts up top, the rears are tacked to the seat mounts, the fronts I can reach so they are nylocks. hope this gives you some ideas. I'm pretty happy with my seat mount, nice and low and, I believe, strong.