Hey this is probably silly but I'm quite concerned with the aluminium getting bent so here's my idea:
1/ Get a batch of steel plates made.
2/ While you have aluminium plates left only ship under two conditions:
* Two plates sell minimum
* At least on of them needs to be aluminium
3/ Tape the aluminium plate to the steel one so that it doesn't get bent in the mail
4/ Ship it!
How does that sound?
)