Yo, DB Fan. Accepting Richard McCoy as DB Cooper requires one to untangle the FBI conundrum - whom to believe and what evidence to accept.
The Seattle office has what they consider proof that McCoy was in Provo on Thanksgiving Day, 1971; ie: the eye-witness reports that place McCoy at home and his mileage logs, such as those Marty has been referring to.
The Salt Lake City office says, "Nope. He was in Las Vegas and probably transiting to/from Portland," and Calame and Rhodes have a ton of evidence to support that perspective, such as gas receipts and a collect phone call.
To accept McCoy as Cooper, you have to disprove the Seattle's evidence. Can you?
More troubling, can Gryder? As Marty has pointed out, Dan Gryder is grossly under-informed on much of the McCoy evidence. Such a state of affairs makes his touting of McCoy-as-Cooper nearly impossible to believe.
In addition, dodging my phone calls AND dissing Darren puts Gryder, Chante, and Little Rick in a bad light. That's two big strikes against Danny G, and one more assigns him to the trash pile along with RMB and Kenny C.