Cyc was his nickname - his given name appears to have been Carlton, but I've also seen it as simply Carl. Sort of like calling Andre "Firestarter" Clouter "Fire" for short. (Speaking of which, why weren't you at assembly in your own backyard, Fire?)
A couple of scenarios - first is it was built "on the side" while the factory was still running. Warning - dream sequence coming up! Imagine Judd Rushton saying to Cyc - "sure you can build an Indian Girl on your own after hours. Just work after hours and use wood from the reject pile."
or, after the factory closes in 1917, at some point assets are liquidated. Leyare in O'burg ends up with rights to the IG name and some arrangement to continue building IG canoes under the Whistle Wing name (and based on styles, with former Rushton contractors). Cyc ends up with a mold, (begs, borrows, salvages, steals), and without a factory in town, has to rely on second quality lumber. (All of the Good Wood is Gone, it's all sapwood and checks for now on" - Sung to the tune of "All of the Hard Days are Gone" )
We do know that for anyone who had been hanging around a canvas canoe shop back in the day, the skills aren't all that hard to learn. Heck, how many current WCHA members build canoes as good or better as amateurs?