I got a hatchery summer steelhead around 6 pounds fly fishing dry flies for the rainbow trout in mid July back around 7 or 8 years ago now. I never did notice if it was max clipped or not, but I released it regardless. Awesome to see that big head come up for a size 16 dry fly elk hair caddis. Who knows if it was an early/late running steelhead, but it was a bullet, and the proportions screamed steelhead to me rather than a resident bow.
Two other memorable summer runs I've caught on the Vedder were both in December, and both were wild.
This one was Dec 22, 2011 at Prison run. The flash made the fish look MUCH brighter than it was. It was in full blown spawning colours. Double striper with a red belly(you can see the faint shades of red by the pelvic fins, the rest was "whited out" by the flash).
This second summer run was on Dec 19, 2013 at Thurston. Again, a very dark fish which would be characteristic of a summer runs teelhead.
As for the rainbows in the Vedder, this is the largest I've caught. I find they are typically a deep fish (fat). I would say TLS's is a steelhead based on how streamline it is. I would also agree with Dave that the rainbows take on more colour, since they live in the system for camouflage. Again, the flash kind of whited out his colours. Fish was caught Dec 27, 2011.