It is a perfect fit.

I got the seat from one of the forum member's and rode for about two hours today with it. It was not as comfy as the Sundowner that I took off
but it sure look's a lot better. I really like the stripped down look that the rear pillion has - it really makes that wider fender look good on my '10 RK.

I had a HD backrest for the sundowner so it was interchangeable with the SG seat. It work's very well on the SG seat and the stitch pattern matches as well. All in all I think that with the longer shocks that are on the RK standard
it made for a very good ride - not as "cushy" as the Sundowner. But a real nice short hop seat. I'm going to let some of the air out of the shocks on my next ride and see how that works out.

I think the seat makes for a good alternative to a high priced "solo seat" and I honestly think it probably just as comfortable as any of the high end solo's.
And as a plus I saved some serious coin by going this route.