Great pattern, and glad to see the article on it. It is a great all around baitfish pattern that swims really well in the water as most marabou's do.... Not having the luxury of steelhead fishing over here in Indonesia I haven't used it for steelhead for over 2 years now... But I did use it successfully on Barramundi in Australia, fished drains in the estuary on outgoing tide....they loved it.
At the end of the day there is no magic fly as we all know.....but certain ones work in some conditions better than others and the Cop Car is one of those.
And if you go back to the late 1950's on into the early 1970's in steelhead fly fishing history to Wes Drain who lived in Everett after moving to Washington state from northern California, you will find that he tied and fished a huge white marabou for winter fish. Drain tied his on very large Carisle hooks (this style hook is almost non-existent today) sizes #5/0 to #7/0. His white marabou was tied either with no body or one of flat silver tinsel, had multiple whole marabou plumes tied both on top and bottom, and had a red or blue schlappen (or other large, webby hackle) tied as a collar over the marabou stems.
In other words, large white marabou flies with red or blue added to them for steelhead are not new. They were used 50 years ago by Wes Drain and some of his friends. The Cop Car differs in its use of Krystal Flash, a material that didn't exist when Drain was alive. Nevertheless, it is an effective fly, just not the first to use a large white marabou fly as a steelhead fly.