You stand to gain MUCH more time by spending more energy while riding into the headwind than when you have a tailwind. It's similar to riding hilly road races - you'll gain much more time if you attack on the climbs, than if you attack while descending. I'm not saying that you should take it easy while you have a tailwind... go hard, but not so much that you can no longer maintain the same average speed once you hit the headwind.
From your course & wind description, it sounds like the wind will play well with the thirds rule. The way I would ride the course would be the same as any other TT I do:
1/3: hard, but at an effort you know you can hold for the whole course
2/3: assess if you can push harder and hold that same pace for the rest of the course
3/3: assess one more time, and again, go harder only if you feel like the new tempo can be held out until the end.
All said... I'm not sure if a TT-style energy dump via thirds rule is applicable to dong a Tri; shouldn't you be saving for energy the run leg? After all, I'm just a roadie that wandered into the tri forum for fun tonight =).
Last edited by digitoast; 07-12-07 at 01:10 AM.