Files is a liar. His shells were discovered in 1987, manufactured in 1971. Unless Files is a time traveler who took shells from 1971 back to 1963, he's full of spombleprofglidnoctobuns. And the shooters were in the pergola, neither of which are James Files. If he had any knowledge of the incident, other than what he read in a book, he would have known where the real shooters were. He's nothing but a con man. The FBI didn't even take him seriously or he'd still be in jail. There's no statute of limitation on murder, and if you're dumb enough to confess to a murder, you'll be going to jail. These things aren't rocket science.
First, let's see your proof. Second, why would conman Files plant a hull from the wrong time? Third, you assume that Files knew the planted hull was a hoax, which you don't. Fourth, how did Files know JFK was struck by a frangible bullet a split second after a bullet struck him from the front causing his head to move back and to the left?
It's not just about the spent hull with his bite mark, which I will reserve judgement on until you post your analysis disqualifying it. Files knew details re the Turkey Shoot, which IMO were borne out many years later. Otherwise, bragging rights aside, I don't see what was in it for him other than a book deal, which never materialized. This case can never be resolved while the conspiracy deniers keep sweeping all potential evidence under the rug in a rush to judgement.