Since the 9" Round size isn't often included in the servings charts and/or how to cut diagrams, I can't seem to find any consistent info on how many servings and the best way to cut a 9" round cake (wedding portion size).  Please share with me the best cutting diagram/instructions and number of servings that you share with your customers for 1"x2" serving sizes. 

In The Wilton charts they portrait 32 portions... I advise you to make you own diagram. Cut a circle in parchment and try to fit as many 1"x2" portions as you can. I found charts like this for ideas, but as you said, 9in is an uncommon one...You are going to have to be creative and do your own. Good luck