Make sure you are taking enough electrolytes, regularly. I'd even go so far as to set a 30 minute timer on your watch. Not enough can cause _so_ much trouble- and you'll be right in the worst heat range...

(I finished 16th out of 42 riders on my last 200k, not because I am fast- I was going about 14 mph, but because I wasn't at the side of the road puking or rubbing my muscle cramps. It makes a HUGE difference!)

Also, it really, really, really helps to put ice in you helmet, bra, down the back of your shorts, etc. Feels good, and if you can keep your core temp down, you can keep moving and not have to spend a lot of time trying to cool off, off your bike.

Good luck!!

Nanci