Papke was a monster inside, he comoletely neutralized Ketchel and Carpentier with mauling, clinching and infighting. It would all depends on whether Fullmer would be able to overpower Papke in clinches or not.
Carpentier was a kid then. Close fight but I can't think of many that could outmaul Fullmer ,who is not one of my favourites.
Few middleweights could ever match the violence that Papke brought to the ring, but Gene may be one of them, no matter the outcome, the fight would be an ATG war