I've always said that the fingerprint evidence, or lack there of, is the smoking gun here. That and the way the DPD handled the crime scene and the evidence.
Of course Day was complicit if he was tasked to examine the rifle for prints. The DPD knew there weren't prints on the rifle so they had to assign Day to deal with that. But that also went for all the evidence and how it was handled. CE 637 is just another brick in the wall.
However, no LNer is going to succumb to your deductive reasoning regarding the palm print. You are dealing with an image of an alleged print, which could show anything Day & company wanted. You can't trust any evidence that was submitted by the conspirators, even if it's a smoking gun because inconsistencies and contradictions can never amount to proof.
What we need is the dermatoglyphic analysis that positively identified Oswald's palm print. If it shows a fake match then that's incriminating but not proof. If it shows a legit match then that's also incriminating considering Day's handling of the evidence, but not proof. Either way, we need to see the actual evidence and analysis before concluding anything. Otherwise, analyzing a low res image of CE 637 proves nothing and will convince no one.
You would be better served experimenting with your own MC and try to reproduce the alleged palm print the way you claimed Day must have to prove your point and advance your claims.