I have one similar to the 3rd, but the steel bar is at least 2 -3 times as think as what is shown. I got it on ebay along with a used Looney seat. Instead of a hole, it has a long notch cut in the steel bar, about an inch long. I ended up making it about another inch deeper to give me more room for adjustment, but it works great. Only draw back is it requires the stock pillion mount. I preferred the solo look before but it's worth it. It goes about mid way up my back but what I noticed most was that it kept me from moving too far back in the saddle, there by easing pressure on my tailbone. Which was after all, the main
intent of changing my seat.