Struggling with Eating

For those of you who don't know,  RAAM is the race across America, it is a gruelling 6000km race.  In order to enter it solo, you have to qualify.  Now there are many ways to qualify, the one I choose is to do a 24hr race and ride 690km in that time.  This is so daunting.  My first attempt is the Midwest 24 on Labour Day weekend.  I have been training since November for this race.  I live in Canada so most of the training has been indoors (I know crazy!).
I am going crazy, trying to figure out what to eat.  I am a big guy, and I need over 600 calories an hour!!  I have tried less, but I tend to bonk after about 7 hours of riding.  How do I carry that much food with me, when I am riding mostly alone?

I am open to suggestions?