I'm not suggesting you switch, just that the hairball formula contains high fiber (that's what helps with the hairballs)... and can also help with cats with chronic loose stools caused by the above conditions.
If the hairball formula is what is really keeping his stools firmer, then any change you make to the diet may lead you to loose stools. Just something to keep in mind if you do intend to transition him to another diet.
If the hairball formula is what is really keeping his stools firmer, then any change you make to the diet may lead you to loose stools. Just something to keep in mind if you do intend to transition him to another diet.