I think it's possible. No direct evidence, though.
No indirect evidence either! 
No evidence - period.
Well, that's not entirely accurate. Here's some of the indirect evidence:
1. McCoy was in Las Vegas on Nov. 23 and 25, 1971. His presence there was a secret.
2. He returned from LV with about 6 grand, and took his family on an unexpected vacation to North Carolina to see family.
3. McCoy is a known - and convicted - skyjacker, using techniques identical to DBC.
The one thing I don't understand from McCoy is why does he do the exact same hijacking method as Cooper or - if he was Cooper - do the same exact hijacking method as the first time? It would seem corny to me for him to do same crime style as Cooper. McCoy is tough, lawbreaking criminal and you're gonna do the same way? The whole reason of being a criminal is to be different and unlike anyone else.
Unless, he did the same style as Cooper because McCoy was trying to cover up for Cooper. That's why I wonder if he knew him.
My guess is that he copy-catted Cooper because, dead or alive, Cooper was the only one who ever pulled off a successful skyjack and was never caught.
I don't recall how daunting McCoy's landing zone was, but it wasn't the PNW. He DID hide the loot, in a culvert, which is why I remain open to the possibility that Cooper did briefly hide all or part of the money, to return to later when the heat was off. (20+ lbs of cash in a makeshift money belt isn't something you'd walk down Main Street with.) Tina Bar would be easier to find again than "the forked tree next to the big white rock" or something, but he couldn't have PLANNED to go there unless he was a genius of orienteering - he didn't know the flight path in advance, no matter who he was. But he would have looked for a spot he could have found easily again, IMO.
I don't believe McCoy was Cooper - he was too different in personality and if I'm remembering right was too short or young or something? He was kind of like Rackstraw - right background, wrong specifics in key areas. Height also lets Dayton off the hook; there were no platform loafers in 1971 - even at 3, I'm sure I'd have noticed them! But what a lot of fascinating non-celebrities this rabbit hole has revealed, nonetheless.
Re: exalting Cooper or other criminals - his effect on the flight crew's lives is inestimable, a kind of mental assault, and it seems to have been purely a money crime, so hardly worthy of hero status by any measure. But I think the fascination with him is different from the fascination with someone like Zodiac - serial killers who kill purely for the thrill of it don't interest me personally because I find them not only abhorrent but also all pretty much the same. Writing coded notes, pfft, teenagers do that for their crushes, hardly proof of any great genius. Can't crack the code? Maybe that's because the code-maker was mentally ill and following a line of thinking no other individual could. "Just felt like it" or "I heard voices" is not an interesting motive, which is why the only true crime I watch concerning murderers focuses on those with actual motivations, however bizarre. Even then, their stories rarely stay with me.
The interest in Cooper, I think is three-fold: 1) He beat the FBI at a time when they had some pretty bad PR going 2) He didn't lose his cool and wasn't verbally or physically cruel, hence the "gentleman skyjacker" mythology 3) While he may not have actually been a "suit" himself, dressing like one, ditching his necktie, and flying off into the unknown with all that money is a romantic image to anyone caught in a job they feel is choking them, which at any given time is a lot of people. The hippie kids were moving into offices; many of the Silent Generation had already dutifully spent decades in the same jobs. I don't think the psychological impact of someone "escaping the rat race" can be discounted. The mythology of Cooper is one of quick, sudden escape, not simply one of crime.
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