I saw this video last night... The main card looks to be a 9x12 maybe a bit larger... A cornerstone ad on the front side and then the standard ads on the back. Towards the end of the video where Gary starts talking how this could be a profit center, and how to SCALE the concept gets super interesting. LEVERAGING BRAND. Basically find cornerstone advertisers that have BRAND to leverage. https://youtu.be/u1jcO9XMIO0
What gets interesting in this is the guy actually says its $2100 per 5000 cards and usually we talk about to get to cost plus profit, but this concept is cost PLUS profit on a whole other level. a win win for both sides.
Well worth the watch