For those of you having issues with using the Ebay standard envelopes for trading cards, here is my experience using it so far. I have done well over 300 transactions and have only had 1 go missing. It eventually posted as delivered but after contacting the buyer, he said it wasn't. I contacted Ebay and they had me fill out the form to get my money back. Only took a few minutes (make sure you have all screenshots pertaining to the delivery and conversations with the buyer) I received my refund within a day although they say it make take more time than that.
As far as what type of envelope you use may be what is causing issues. I am using an A-2 top flap envelope which is just above the minimum size with either two 110# index cards or #100 cover cut to the size of the envelope depending on the thickness of the toploader I have to use. I also made a 1/4" cutout template to make sure it isn't too thick.
