I asked you this:
Do you have an answer?
You also asked me what the "If I Ran the Zoo" fallacy was. I've taken the time to answer you, but you don't seem interested in such fundamentals.
And of course I have an answer. I'm an attorney and a law professor. First, the "chain of custody" is a requirement of trial courts for ensuring that evidence was not faked, altered, or tampered with before it was brought into court. Oswald never was and never will be tried in a true court of law. So you must ask yourself whether such a forensic standard is appropriate for what is and will always be a historical question. Historians, in their reasonable judgment, accept many forms of evidence that were not hermetically controlled by some chain of custody.
Second, even if we apply a forensic "chain of custody" standard--that is, the procedures that would be applied by a trial court--you are not entitled to establish the standard in your own arbitrary manner. It would be established, of course, by what the courts do and say. Here's what a recent (2017) Texas appellate court stated: “Any gaps in the chain of custody go to the weight of the evidence, not admissibility; however, proof should be shown as to the beginning and end of the chain. [....] The trial court need only make the preliminary determination that the proponent of the item has supplied facts sufficient to support a reasonable jury determination that the proffered evidence is authentic.”
So, at trial, evidence is not automatically ruled inadmissible by a court, even if there appear to be gaps in the chain of custody. The present Texas standard is "facts sufficient to support a reasonable jury determination of authenticity." A reasonable chain of custody may be, and often is, established by the testimony of officers, particularly where defense counsel has challenged documentation or procedures. FBI, Secret Service, and DPD officers would have testified regarding any gap-flawed evidence in the JFK case.
And do you notice that little bit about gaps usually being a question of factual weighting, to be tested by the jury, not a question of admissibility for the court? Even evidence with custody gaps may be admitted upon proper testimony, and those gaps are simply for the jury to assign the weight to be given to the evidence in the final verdict.
Most CTists suggest that the evidence against Oswald, if flawed in any respect, would not be admitted for jury consideration. Not true.
Now, I've answered your questions, but you haven't answered mine. (1) Why do you apply a trial standard instead of a standard appropriate to historical inquiry? (2) Where do you get your standard of a "solid" chain of custody? (3) Why do you feel that the "material evidence" in the JFK case would fail your standard (even if acceptable as a standard)?