Hi Gran - I was told I HAD to use the big white form all the time too. Nothing else would do.
Went to a different PO and was told the same thing. Then the clerk, whose a very nice lady, said she'd look it up tho and then said Oh Wait. Under whatever the weight is, you can use this little green one. Guess it depends on the PO - like everyone says:)
But on small boxes - I've sent video boxes - large and small - as well as that little 6" cube one with the big white customs form on it and the PO clerks have always been able to put the form on them. They don't even hesitate - so I guess I'm not the only one sending them:)
Anyway the cubes are good for sending mugs to a single Soldier - and tough to keep the weight down once you start packing stuff in and around them:). Hope this helps.
Happy packing,
Ann