I'll just say this in regards to a 28" searun cutt. If you did indeed catch a cutt of that size, it was likely a steelhead / searun hybrid.
As far as it being 5 lbs, a fish that length would likely be in the 7 to 8 lb range unless it had spawned recently.
5 lbs at that length would be a real thin, snaky looking fish.
I've fished for them since the 60's. The largest I've ever been fortunate enough to witness was a 24" specimen. A fish of a lifetime and one I wish I'd had the enjoyment to caught myself.
It takes a long time for searuns to get big, so any searun cutt over 20" is a true trophy in my book.