I had the unbelievably good fortune of finding a brand new OEM two up seat on eBay for $80 because it had a slit in it. It was from a dealer that had just received it and it had a 1/2 inch slit in the back somewhere. It was barely noticeable really. I had been hoping to find one at some point, but this one just fell to me before I had started looking.
Anyway, I didn't take pics of my first effort, because it sucked. I left too much of the back piece on in an effort to try and use the first seat clip on the rear fender. Kind of like the factory solo seat looks I guess. All in all, it didn't look good. I took another shot at it and followed a line that was built into the seat back. I went back to the forum and checked out the pics I had seen of Sanderclause's custom seat. Following his example, I found that the leather made a much more natural fold around the new shape. All in all, it looks pretty good. Thank you Sanderclause for the advance work on this one.