Well it is now pretty much buy 2 get 1 free :-) Which I would go for, I'd even forgo the 0.002 you'd make. Put it towards the beer you'll undoubtedly need.
2*0.1 = 0.2
3*0.066 = 0.198
1BTC @650USD = 1.3usd left over (0.02).
It will probably stop you having to mess around with refunds and resubmissions.
mark
That will work for small orders. Because I would have to give 25 for free to dave111223 because he ordered 51. Not thst i dont want to give him for free, it's just there will not be enough usb to give out.
If there's no other method then i'll have to refund.