Robbin -
You're right - the warmers work better under your shorts. As far as layers go,
- if the temperature is above 50 degrees, I usually wear my knee warmers.
- if the temperature is in the 40s, I wear shorts with (kind of insulated) tights over them - my favorites right now are made of Polartec Power Stretch.
- if the temperature is in the 20s or 30s, I wear my shorts + knee warmers + my Power Stretch tights.
What was the temperature on your ride when your butt was cold?
Oh, and if you're interested in the Power Stretch tights, they are on sale at REI right now. You should be able to easily find them by searching for Power Stretch Tights.
--- Denise