3 month old overeating?

Hey ladies, i have a 3 month old and he has been having 5oz of formula every 3 hours with a total of 35oz in a 24 hour period. He was 8lbs5oz at birth and is now over 15lbs and is in the 75th percentile for weight . We want to move him to every 4 hours because he seems like hes getting distracted and maybe not super hungry at the 3 hour mark anymore. My husband wants to move him to 6oz but im suggesting we keep one of the bottles at 5oz so its still 35oz. I dont want to over feed him or give him water poisoning as i know we are already at the upper end of the cutoff. What do you guys think? How much are your 3 month olds drinking?