As Gryder covers in great detail, the FBI had reason to CYA, which probably explains their claimed "evidence" of McCoy being at home. Today, no evidence. Zero. Where did it go? Oops. The only remaining/extant/verifiable piece of evidence from the FBI files was the sister-in-law's deposition, which she now denies (because her sister died and no longer needs family protection). It's all too obvious.
Mc Coy's sister in law now says they were gone for 4 days, and the kids confirm they were babysat for 4 days over Thanksgiving. All too obvious. Unless all three of them are flat-out lying. Yes, possible. Probable? Not in my estimation. Especially after watching their confession on video. If those kids are lying on the Gryder video, I would be shocked. I sense no pretense. Zero. I sense honesty, contriteness, and two kids finally able to get it off their souls.
So, yes, I absolutely believe the sister and 2 kids rather than 50 year old missing "evidence" that probably never existed in the first place.
Enjoy the hunt, but in my mind, it's McCoy. Heck, he did the same freaking highjacking on another flight (!!!) and the myriad parallels between the two flights are irrefutably the same methods.