I live in Australia. The G-Cat does seem to have similar lines, but the photos I have found so far aren't clear enough to ascertain how similar. I wouldn't describe it as "Dart-like" though, at least based on my limited knowledge of Darts, but I should look into them some more as well.

I have assumed this boat was along the lines of what you suggest - a backyard job by someone who knew how to weld, and wanted a cat. However, I have tracked down two identical cats, and although the owners couldn't tell me anything, I was led to believe that there are at least 2 or 3 more. Which is a tad more serious than the usual backyard job. Also, the surprising speed and nice lines suggest that it was probably made fairly seriously, by someone who knew about boats.

My only lead before the help I was given here was that the last owner believed it was based on a Sabre Cat, but that now looks very unlikely. There is a manufacturer in Western Australia called Sabre Catamarans, but they make 80 foot high-speed ferrys, so unless they used to make something considerably smaller I suspect it isn't them.

At any rate, thanks for all the help. Luck holding I'll be able to get it into the water in the next week or so, and I am looking forward to testing it under race conditions. I'm not sure if an aluminium hull will prove to be a benefit or a liability, but it shoud be interesting.

Thanks heaps!