Interesting subject & one that is discussed on an occasional basis.
I include 2 photographs for my response to this thread.
The 1st is of a female Snow corn age approx. 15 years who has, over the years, provided excellent progeny & continually double-clutches which has it's effect on her weight.
She is 760grams at this time having regained some body weight since last Season.
Do remember that this female is not consistently bred each year but she will still provide a double-clutch of infertile eggs which alters her overall weight during the year.
As you may observe she is in excellent health & I consider her body fat to be just about right, a little extra weight would not go wrong either!
The next photograph is of our 1st corn, the infamous Mulder who is a typical male during the Breeding Season with reference to a reluctance to feed.
He is 918grams to date & to be honest I would prefer a little more weight on him.
He too is in excellent health & at approx. 17 years of age still 'sports' that attractive appearance that appealed to us in his younger days.
The female is fed weekly / fortnightly depending on the size of the food item, which is usually our own Breeder Mice.
The male is fed when he will accept food & he too enjoys Breeder Mice.
My concern here is that your male is at best 5 - 6 years old & is already quite a sizeable animal.
As very few folks retain their animals for their entire life-time there's not much iformation out there on the ideal mature size / weight for a corn snake.
Regards. Lex