Usps flat rate boxes

I calculated that a lead ingot cast in the shape of the small flat rate box would come in at about 68 lbs... (as in, just barely under the 70 lb weight limit)
(yeah, the USPS pissed me off, and I was thinking about going into the bulk lead reselling business on ebay to square things up, but they finally paid my claim 3 months and 3 weeks later - yes, sometimes I'm petty enough to at least research things :) )