That sounds totally perfect. I think you would have a very easy time adapting it with the frame and fittings - my transom is flat and I believe yours is pretty much flat, too. I am happy to send you pictures if you like so you can make some decision.
Like all wind vane steering
, it depends on wind
being from a relatively constant direction. This unit takes a bit of doing to set up, but once on-line, it's really easy to manage (you can even set it up so that you can change course remotely with a line, but I never did that).
I'm in Connecticut, so if you're near Stamford, stop by at any time. If nothing else, you'll get a glass of wine and we can share stories (probably yours are better than mine, but I'm working on it...)