I make those 1/16 scale 55 gallon fuel drums out of solid steel and they weigh about a pound each and I can put ten of them in a small flat rate box. That got me a few weird looks at the post office.

But USPS is still the way to go for me, too. I have an account now so I can print labels and pay with paypal and up to a medium flat rate box will fit in my big mailbox and the mailman picks it up right here at the house. Just not having to drive down to the post office or the UPS store is invaluable.