I feel your pain!
My coldest ride started out at 18 degrees and ended up under 10 at the finish. It was the first time that I HATED downhills! I actually got my hubby some of these, kind of as a joke because he was always complaining that no matter how many socks he wore, the type of booties, etc., his feet were always cold.
http://www.amazon.com/BeWellShop-com...UTF8&s=apparel
Well, the joke is on me, because he loves them and thinks that they work really well.....So if you are planning on going winter riding a lot and with your having frostbite on your feet, you might think about trying them!
The best rides are the ones where you bite off much more than you can chew--and live through it.