corn is straight carbs so what it adds is fat. Personally I mostly do without it.
I was getting ready to do a feed experiment feeding one batch all corn, just to watch the weight gain etc. but my processor talked me out of it, he sees more butchered birds in a week than we do all year and he's been doing it for 30 years so I really trust the advice I get from him. He said he has seen plenty of corn feed experiments and that he truly does not like the carcasses, say they have really yellow slick fat all over them and that the insides are all fattied up looking ready for CHF.
I took his advice as I have yet to see any CHF in mine and I feed 20% from start to finish. So I guess my thoughts for you are; you're on track don't mess with it.