I don’t know the harvesting protocols for fuel corn. Maybe be similar to silage harvesting.
Silage is generally harvested on corn that hasn't produced all that much in the way of Ears. While I don't know what all farmers do, this is what all the farmers I know did. I know that silage general came from corn that was sorta short growth(like 60 day corn or whatever) and was harvested after 45 days.(something like that)