Congrats on your GS Phil -
We have not had one of the lighter GS's but did enjoy the twin engine on our 11 RT for over 70,000 miles before trading. I would check out your options and if happy with your Can Am dealer and prices, stay with the Kendas. I take our wheels off and have our Discount Tire shop mount our tires and balance the fronts (have balanced the backs by hand) but have run OEM Kendas, a set of Michelins, 2 sets of Kumhos (F&Rear), several rear Kumhos, and now have a couple of Generals to try. We had some early balance/vibration issues on our 11 RT with a Kenda, and the quick wear out of the the Kenda rears especially the 2014 rubber compound, but I have run Kendas on two wheelers and I think they run okay.
I run the Kumhos mostly for their 25,000 mile wear life and good roll, and have put most of our 170,000 plus Spyder miles on Kumhos on the RT's. Right now I have a full set of Kumhos on my 15 RT, and the wifes F3T is still running the OEM Kendas on front with 20,000 miles so far, and a General Altimax on the rear for the last 7,000 miles plus. If you want long wear life and want to spend the money, look for that in a tire, but any of the tires mentioned have some features that people like, OR have a local supplier that people like to use. Your choice, just enjoy the RYde. Many more miles and Smiles on your GS!