How important are the seat pan risers to the structural integrity of a 66 coupe? I bought set of 07 Shelby seats but they site too high on stock risers. I was going to do the pan drop but I don't think that will be enough. I want to keep the power setup for the drivers seat so modifying the seats to use the original tracks is out. My thought was to weld 1" sq. tubing across the actual pan and bolt the seats to them. Any thoughts?

I've installed new floor pans already but the seats I'd like to use will be too tall if I install the seat risers. I'm looking to lower the seat by about 2 inches which cuts out almost all of the rear portion of the riser. The tracks on the Shelby seats are longer as well so the rear seat track holes won't be usable. My though was to add some sort of structure to mount the seats on so they're not directly on the actual floor pan. I was thinking 1x2 sq tubing welded to the pans then the seats mounted to it would be sufficient. I'm concerned as to how much the seat risers plan into the structure/rigidity of the overall floors and car.
If I could get a hold of a metal brake I'd make my own risers to work with the seats.