i had the same setup as the pick above. The sundowner with a backrest for my wife. It was super comfortable for both of us, but like others say i think its the ugliest thing ive ever seen. This might be a good excuse to get a different bike if youve always wanted one.

 

Our 1st Harley was an FXDXT,the standard seat was pretty comfortable,but the Nose fairing used to buffet my glasses off,so I decided we needed an Electraglide,so bought an Ultra,mistake it felt like a land barge & my wife was more comfortable on the FXDXT,because the hard bags dug into the backs of her legs.
So we bought the FatBob & fitted a Sundowner with the Massive detachable touring passenger backrest,both of us are more comfortable & we both prefer the Dyna to the Ultra,it just feels more like we're riding a bike.

 

I put one on my Dyna. Yeah, ugly in the sense that it looks out of proportion. It is much more comfortable than the stock seat, but I wish the Sundowner placed me an inch further back.

 

I put a Sundowner on my LowRider, and my wife is much more comfortable on it versus the stock seat. With that said, it still isn't exactly the ticket for long range touring, and the Sundowner also sets me a bit forward and higher than the stock seat does (not really a good thing). The nice thing about it is, it only takes about two minutes to switch the seats. I generally use the stocker for commuting and for any other solo riding.