i used a piece of aluminum across the back which is easy to do. the hard part is the bottom, you need to make a brace across the front similar to the shape of the seat and bolt it down to that.
sorry no pics, i removed it all and put my back seat in again!
Yeah I did a backseat "delete". I unbolted it and put it in the basement. Now you see the factory sheetmetal floor, caulking, and seat belt bolts. Oh you wanted something that looks good?
The fastback seat is more like 65lbs. I had tire rubbing issues and removing it really helped. Once I get new rims/tires with the right backspace and fix my fender I'll put the backseat back in. It would also be nice to actually take a ride with the kids, who weren't born yet when I started work on the Mustang.