I don't think the seat will fit from the 650 R. I think the sub frame is different. There is one member on here that knows for sure. He hade a real nice Versys type bike out of a 650 R. I am not sure why you would want that seat. I had the R and hated the seat after 50 miles and the V seat is not perfect but much better and flatter than the log shape of the R. Is only my perspective. Your butt may be shaped different or younger.
Yamaha Secca II
Life is not a practice run. Enjoy each and every day.