Hello therecordingart,
I've just had a look in the shipping options in the cubecart (the open source web-shop we use).
Flat rate box was originally chosen because we started out with the metal API500 cases, and I was concerned about the envelopes not being strong enough.
Small flat rate box isn't available as an option in the shipping module. I'll continue to look into it, and once the update comes on to cubecart, update appropriately.
Your more than welcome to wait for Bryan to get these boards in, they should ship to him over the weekend. If your only building one-offs, it seems that his service is a better one to get boards from. He works out cheaper than ordering from multiple suppliers, overpaying, then paying shipping on each piece.
Cheers
Rochey