Hanging the frame up until the correct post has been obtained is definitely the best advice; the problem is I doubt I would have the self-control to follow it.

What I would end up doing is going to Kroger's and buying an disposable aluminum roasting pan, and cutting two inch wide strips from it. I would sand the non-stick coating off one side of the strips. Then I would figure out how much of the strip needs to be wrapped around the circumference of the seatpost to achieve a snug fit. It is probable that I would then superglue the strips to the seatpost, one at the bottom and one at the cinch area. When the correct seatpost arrives, i don't want to spend half the day trying to dig this homebuilt crap out of my seat tube; more importantly I want to be sure that the shims stay in the right place. I can tear them off later if need be; the superglue residue will stick to the seatpost, yes, but that is preferable to it sticking to the aluminum strips and yanking off chunks of epoxy matrix from the seatpost. If later re-using the seatpost on another bike, I would simply gently file the superglue residue off (you would have to file pretty deep before
you hit carbon fiber) and seatpost is ready to serve.

While i wouldn't wrap roasting pans around the nose of the space shuttle, I know its at least as tough as seatpost resin, i've used the same stuff to shim seatpost rails for an optimum seat angle- which is a far greater compression load- and it works fine for that.

This is definitely not what I would advise someone else to do, though. I just know I personally wouldn't last five minutes before burning rubber to the grocery store baking supplies section.
Gerry