The location is not an exact science.....put your hand around the tiller like your steering the boat, and I installed the extension socket a couple inches behind where my hand would be. I like the long Forespar tiller extensions because they are adjustable, and have the the mount in the tiller so they are removeable. These also allow you to use the tiller cover, and with the long extension, allows you to sit forward along the cabin bulkhead so the boat sails better, (weight forward= better performing boat).
I LOVED our C-18! One of the Best unknown boats out there!!! Can't understand why there ain't a lot more of them out there!
The attached photo shows our C-18 moored at Two Harbors during one of her trips to Catalina Island.
Don