HRoth - 12:33 pm on Mar 12, 2012 (gmt 0)
I have found that if it's in-state or a contiguous state, it is cheaper to ship plain priority, but everywhere else, it is cheaper to ship flat rate. I have been using the small flat rate boxes when I use flat rate, though. You are right that the bigger ones are generally no bargain unless the item is really heavy. A friend shipped me some railroad spikes in a flat rate box: worth it!