cereal in formula

Emma • I`m Emma. I`m 23 and happily married to the love of my life. We welcomed a baby boy 5/13/16 by emergency c-section!
My husband and I want to add some cereal to my 4mo olds bed time bottle so he will be a little fuller and sleep longer maybe. He takes a 6oz bottle before bed how much cereal should I put in?  
Thanks mamas!