I converted my '06 back in November to a RS.
The speedo was off like everyone else's. It's not a RS thing, it's a Honda thing.
I got used to using my GPS, which is dead on when it comes to the speed read-out, and then noting the GW speedo to get a feel for the difference....about 4 MPH less than indicated.
I had one major issue with the RS kit and the installer immediately made it right. I had a broken trunk lid right where the lower left hinge was mounted and it was broken really bad...it completely came apart at the break. They put on a new lid. All the "other stuff" was minor installer issues, not RS, and I fixed most of those myself. The rear-end/CVs in these conversions are built for cars and a GW trike should not ever be a problem, but anything mechanical can have an issue, I guess. I believe RS will do you right.
Like many, I literally hated it after the conversion and cussed myself daily for destroying a perfectly darn good GW. I probably would have sold it but it was the only way my wife can ride anymore so I kept it. I eventually got to where I tolerated it, then I sorta got to liking it, and now I love it. It's our long-distance machine since it is the only way my wife can ride. For running solo, I have a '14 Yamaha FJR....LOL. I'm 63 and people always look at me weird when I take my helmet off and get off it. One guy actually asked me how old I was and I told him. He asked me why a guy my age would be riding a "sports bike" and I said told him that I totally got off riding it...it worked better than the blue pill. He just walked away shaking his head.
Once it's fixed, I hope you get to liking it and enjoying the ride. Keep us all posted.