I will be mailing myself food for the Trans Am Bike race. Thanks for the heads up about checking PO hours ahead of time. This works for me as I prefer organic foods and sources of energy that are free of standard commercial toxins. Since I have a map of the exact route and a rough goal of my daily mileage, I am planning to send three boxes at 1000-mile intervals.
Some food for thought on that from someone who has used drop boxes and who has ridden across the country and done other similarly long tours...
I am having trouble making sense of your plan. You describe it as a race, but 100-120 miles per day does not sound like a race pace. It sounds like a lot of mileage for a tour but not much for a race. What race race you referring to? RAAM?
It is your ride and your choice, but 1000 miles worth of food at a time sounds like a heck of a lot of food to carry at once. This is especially true if you are racing.
Then there is the mention of Cliff bars per box...
Cliff bars are generally pretty available along the way on the routes I have taken across the US and much of the way on my rides has been about as rural as it gets. You will be stopping for water and/or other beverages any way and these days most mini marts, walmarts, targets, and convenience stores all usually have cliff bars. I doubt that finding them would involve much/any searching. I could see possibly see using drop boxes if your diet needed to be something hard to find along the way, but for the cliff bars I definitely wouldn't carry too many days worth at at time, they are just too available for that.
Besides that, I know that the folks I have toured with and I got very sick of of cliff bars after a few weeks on the road and we were not eating the 10 or more per day you mention.
Another problem I can see is that when touring getting to locations where you have a package to pick up, I seem to fairly often wind up arriving there at at time the post office is closed. This was true for us even when planning only a few days ahead at a time. For a race it seems to me it even more likely that you might wind up arriving at a time the post office is closed and waiting around for them to be open would be less desirable than when touring.