Some people simply use a bungee between the tiller bar and rearbeam. This bungee has tow ends connected to the tiller bar and its middle to the rearbeam. I looks like a flat V.

Pretty much these are all systems that make the boat track straight while you have layed down the tiller extention and are hoisting or doucing the spi. If you want to boat to track through a curve then you just add some friction to the system so that it takes a small force to change the angle of the rudders. One that is just to large to be overcome by the rudders themselfs. These systems require well balanced rudders, but when they are it is always a pretty simple mod. I know of several different versions. Most of these can be home made and only involve 3 or 4 very basic parts.

I feel truly silly discussing these ludicrous simple systems as "Self steerage systems". I consider the automated steerage systems as used on yachts as true "self steerage systems" not some bungee or rubber connection on the tiller bar.

Wouter