Tom,
There were only 3 18's competing at Mile High, none magnums or SX's. We raced in the open class, apparently there were 5 boats preregistered: 3 18's and a couple of the modern plastic cats, (sorry, don't remember the model names) but the plastic cats never showed that I know of. I believe there were 41 boats total.
I also raced a 16 back in the mid '80's and was up at Mile High several times. I wonder if we ever raced each other?
There was plenty of competition up there for a beginner sailor like me! One of the other 18's seemed to have it all dialed in pretty well, I think his name was Dino or something like that from Oakhurst. The only time I was anywhere near him was at the start! The other 18 seemed to have a lot of issues, and I don't even remember seeing them during the first couple of races on Saturday.
mike bennett
'81 Hobie 18