Along with the bodywork, the seat was too squared off for my liking. I spent way too much time deciding if I should get a fiberglass tail or try to reshape the original pan. After devising numerous methods of reforming the radius in the edge of the pan with the right contour, I decided to cut and paste instead.

I came up with a template of a shape I thought looked good using a CAD program and laid that out on the pan (black line). I spent quite a while thinking about the best places to cut to get everything to match up so it could be butt welded nice and pretty. I finally realized it was a seat. There was no need to get perfect joints on this rusty tray that would be hidden under foam and fabric anyway. So I laid out the cut lines (pink) freehand and started cutting. Soon I was just cutting where it looked to make the most sense. When the time came to form the shape, I ended up eyeballing it and not matching the template I had spent so much time drawing. I made a new template from the now modified side and used that to check the shape of the second side.

Once the tank arrived I modified the front of the seat to fit. This tank is longer with a broader back edge than the stock tank, which made cutting the base pretty easy. Once I got it close, I transferred the outline of the back of the tank to the seat base and trimmed to fit.

I'll still be able to use the stock mounts up front, but I did modify the rear mounts as the base will now sit slightly further back than stock. The original mounts were pretty beat up anyway, so this wasn't a big deal.

Clockwise from upper left: Stock seat base. Lines laid out and cuts started. One side shaped, one to go. Base more or less at final shape. Another view.