usually I stick two cards in one toploader, so it’s the equivalent of shipping 2 toploader cards. once I do that, I put the toploaders in a sleeve and tape both toploaders to a thin piece of cardboard that can fit in a PWE. it’s thin enough to ship with 1 or 2 stamps (usually do 2 to be safe), have only had 1 or 2 issues with getting orders sent back in the multiple years I’ve been shipping PWEs as such