You would still have to replace the 40 hole hub with a 36 hole if you went that route.
I’ve only used one version of the 635 tire on the bikes that live here. The Schwalbe “Marathon” tires are installed on both of our Roadsters, my son has run them on about 5 Lake Pepin Tours, and used his Roadster as a daily training regimen for his high school mountain bike racing team endeavors. Pedaling the Roadster about is like pedaling a dump truck when compared to his carbon fiber Orbea mountain bike, and a more intense cardio workout. I have no reason to doubt this.He has a bunch of miles and hard use on them, and there is a bunch left. They wear like iron.
One could lodge the complaint that they weigh like iron as well, but, if you are on a Roadster, weight likely wasn't very high on your list of concerns, just guessing.
Somewhere between 60 and 63 years of age, I came to the realization that riding a Roadster on the Tour was a decision that left you struck with consequence. The boy, makes it look easy.
Ted