Suggest that you take a look at the installation instructions for the Feathercraft Rudder System.  Go into the boat gear section here and find the Feathercraft Rudder.  There is a link in the description section.  Generically speaking, you make sure that you have a big end pour then you cut off a little of the stern.

Adding a rudder is certainly an item of individual preference.  That being said, I could not find a single picture of a SS with a rudder.  If you look through the pictures, rudders are even rare on 16' kayaks.  My flea weight wife (novice paddler) does fine in her CH16LT without a rudder.

I just installed the smart track system with the long pin on a West river 18 I am building for my brother. I ended up ordering the rudder mount bracket from CLC. There was no way I was cutting off part of the boat to install "optional" hardware. I would reccomend ordering one for your build, there really is no feasible option, unless you were to order the feathercraft.  Also, before you install your footbraces, check the cable lengths. On the set shipped to me, one side was 24" shorter than the other. Joey at CLC told me that I was not the first to have this issue and shipped a replacement at lightning speed. The worst part was removing the footbrace that I had already installed on the footbrace mounting kit studs with nylon lock nuts. It is quite the stretch!  Good luck!

   I'm no expert, but I have this boat as well and I wouldn't consider putting a rudder on it at all. I've read somewhere that West Greenland style kayaks are meant to weathercock to some end...has something to do with seal and whale hunting...but I digress! I've paddled my boat in all manner of weather, and have never felt the need for a rudder. Yeah, some creative paddling in a crosswind is necessary, but for me that's part of the allure of the sport. 

Have you considered a skeg instead? I think that there are kits that can be put on our boat. 

Just my humble 2 cents...but if you're set on having a rudder, let us know how it works...would be helpful for those considering a build to know that it can be done...

   I have a Shearwater Sport, and I can't think of an occaision when I wished it had a rudder. I've paddled it in sea, and wind. I've also used it with a sail rig (Flat Earth), and again, no need for a rudder. I think it would be a whole load more rigging to fix up, get full of sand, scrape on the beach, for little benefit. 

Just my two penn'orth though, as I haven't tried one with a rudder - maybe it will be ace.

   You might want to wait and see if a skeg or rudder is needed.

How to Choose Between a Rudder and Skeg

I bought rudder kits for a shearwater 14 and sport I built side by side.  Learned later I would need to cut off a bit of the aft to make them work.  Decided not to because I really liked the lines of the boats and have not regretted it.  The boats paddle very nice and track straight.  Check out my earlier post " shearwaters launch".

   my 2 cents....don't put a rudder on it.  not necessary....keep the boat simple...i think it wrecks the lines/beauty of the boat.

   Hey guys thanks a ton for the comments! very helpful! After reading the comments, I decided that I would not install the rudder. I am going to have my stepmother try it out today, which happens to be the day we surprise her with the boat and it's first launching. My father and I both agree that if she really feels the need for the rudder, we'll install it. I hadn't thought much about a skeg but it sounds like that may be something she'd be interested in. I'll see how it goes today and I'll let you guys know. On a side note, I did a time lapse build of this boat. I'm working on uploading to google right now. Keep your eyes peeled for a new thread with the video of the build. Overall about 7900 photos and about 72 hrs of build time. Thanks guys.