I know this doesn't answer your orginal question but you might consider spending some this reading up on sheet to tiller selfsteering.
I own a contessa 26 and have had some success this past summer using it, day sailing on Lake Ontario. it is not a perfect solution to self steering
but can work quite well with practice, no electricity needed.
See links below as a place to start.
John
Sheet-to-Tiller Self Steering
A Pearson Ariel Page