I have made a device to help steer the boat when single handing. I bought an adjustable aluminum pole that came with a brush on the end. (It was only about five dollars or so at Big Lots) It is somewhat like a forespar tiller extension. It has a ring that you twist to lock the extension to whatever length you want. I made a pin that fit the existing hole in the handle end of the pole. I mounted the pin vertically near the toerail. On the other end I made a U-shaped fitting that fit my existing Spinlock fitting on my tiller. I can quickly disconnect the tiller extension and it is easy to adjust and lock.
Unfortunately when you think you have the tiller adjusted to steer the boat straight ahead - your weight moving forward on the boat changes the balance and the boat will eventually end up turning- so you usually have to move pretty fast whenever you go forward.
