I dont think you can get any factory parts for the Atoms, but if it is all there when you buy it you can fabricate any part you may need in the future.
I own one and would not own anything else. If I were to give it a downside I would say that it is a little delicate sitting there on the transom but I am talking about someone bouncing off the boat and damaging the Atoms, not that it is delicate in its workings. For as light as they made this self-steering device it functions very well and is very durable.
You will need to have some spares fabricated for the Atoms if you plan to go off shore. You will need extra windvanes, an extra paddle and some spare small parts. The most delicate part is the drag link that connects the windvane
on top to the bell crank on the paddle assembly. This link is pretty light and the ball joint connectors on the ends can fail. I carry extra ball joints(machined myself from acetal ) and an extra drag link. The ball joint on the top end of the rod usually fails because of UV exposure over time.
I think this windane is pretty easy to set and steers my boat well, even overcomes some pretty stiff weather helm
at times. I have a bigger vane that I use for downwind and it helps to a point but like them all, you still need apparent wind
to get it to work dependably.
I like my Atoms. You should have no problem with it handling your size boat. If you need any help getting it set up or want to talk about parts and whatnot, feel free to PM me.