Hint from someone who has literally shipped two tons of lead.
weigh out 65 lbs of alloy.
get a med flat rate box.
get six small flat rate boxes.
use elmers glue to glue the bottom of the MFRB, then tape the bottom closed too.
make up the 6 SMFRB's, tape them up after adding the alloy, use newspaper to fill the gaps so it doesn't rattle.
tape sides of MFRB, then, amazingly add 6 SMFRB's inside the MFRB.
glue the top closed and glue it to the boxes inside, then tape the top.
label as EXTRA HEAVY, add shipping label
done.
That's not bad and is well thought out.
I have a similar approach, but I've had damaged packages in the past, and they are are not that uncommon if you ship a lot of stuff...even one will piss me off.
I hot melt glue the boxes and put the internal boxes inside the Tyvek envelopes that they have for international shipping and others, wrapped tightly around the boxes and taped solid. Sometimes I have used 2 of the same sized FR boxes one inside the other to get a double wall.
If there is more than one internal bundle I glue the Tyvek bundles together to form a solid-one-piece insert. I might glue the insert into the external box, and tape the outside with a minimum of 2 doubled bands of packing tape circling both dimensions. Heat welded plastic banding is a similar concept and even better.
Taped boxes boxes are ok until USPS manages to get them wet somehow and drag them down a warehouse floor and spill your contents everywhere and the cardboard has all the strength of wet spaghetti...btdt!
The damaged and partially missing shipments I have had in the past would have arrived intact had I adopted the Tyvek envelopes and the other procedures sooner.
Whatever method you choose, keep in mind that if you think it's overkill, it's only overkill until it's needed. Whatever works.
I always buy insurance and tracking, and return receipt if expensive, but consider how you will prove contents, condition and v alue to the USPS satisfaction when going through the USPS claims process that takes 30-60 days. They will ask for satisfactory proof before they will pay out a claim.
I take pictures and keep sales receipts, etc.
I generally like my local USPS and they are pretty good but damaged/missing shipments piss me off.
UPS is worse, but claims are simpler, but just CYA.
