Yes, the subframe is no problem at all on the WR. It's strong! The Seat Concepts is a WINNER! I can ride mine all day, day after day, have done so, and no problem.
As for gearing, I'm reluctant to go down on the CS sprocket as some have had problems with the chain getting too close to the WRR's swing arm and chain protector. Also, the larger you can go on the CS, the happier the chain will be. I prefer to go up on the back and get a longer chain. I ran 47 on the TAT, and would go with 50 if did it again. Not only does that give you the umph to get up the tallest peaks in the thin air, but it will let you use third gear in many places where with the 47 you are either screaming in second or lugging in third. The 50 will also let you use 6 on the highway, loaded, and still do 65mph all day long. My chain of choice is the DID X-Ring Gold. Very durable and no noticeable stretch over 8500 miles of the TAT.