I include this picture as the flash brings out the silver piping well so you can see the backrest well.
We have the Yamaha topcase with backrest and the Corbin Canyon Dual Sport with backrest.
This photo is included so you can see how the Corbin backrest works with the topcase pad to provide both lower and upper support.
This seat is much better than stock on the long haul. If you are into maximum long distance (400+ mile per day) then go with the Russel, or Mayer solutions. We have done an 863 mile day on the stock seats and the pain was significant. My problems with the Corbin is that it seems to make the heat issue worse by heating up quite a bit itself (fixes in action and I might remember to report on their effect), and I have taken the Corbin on 600 mile days solo with no problem, but we get a bit of butt soreness after about 250 miles on the corbin if we don't take breaks and stuff. I think the Russell would be better...but maybe I should just take more breaks.
We started with the topcase with backrest and it worked well with one major problem. Momentum from bumps threw the topcase forward so fast that it would thump Sherri very hard if she wasn't leaning back on the case. It hurt her sometimes!
In comes the Corbin with the backrest (yep, fits right in and the backrest pivots forward so you can open the topcase with the backrest in place). The backrest prevents the topcase from flying forward and there are no more thumps on Sherri's back. Also, the corbin provides lower back support, and works well with the topcase pad as Sherri can lean back and get upper back support as well!
We're happy with the solution and although I would like to look into Russell and Mayer, they would have to solve the backrest issues as well as the corbin does, or we wouldn't go that way.