I'm in the process of becoming fat adapted for endurance cycling. I think a lot of your question boils down to your heartrate. Are you trying to win the race or just complete it. If you are just challenging yourself and can stay below 70% of your max heart rate during the race, then you probably don't need to "carb up" for the race and you can use your existing fat stores for fuel. If you are going to be anerobic, then you probably need to top off your glycogen stores prior to the race and may want to consider fueling with carbs during the race. I guess it really just depends on your goals and what you are trying to accomplish. I'm aiming to eliminate the GU packet/sugar fueling if possible. We'll see. Good luck!