I tried using some aluminum tape under the seat with no noticable improvement. Then I installed a woven aluminized automotive heat shield fabric under the seat and that made it worse. I guess applying it directly to the seat the only adds to the conduction. Took it off after the first ride. Next...
Thanks. I've contacted Yamaha to raise their awareness of the issue and will be taking it by the dealer to get it checked out. It's too uncomfortable to keep riding, and it's brand new!