I've been working with Waltly for a custom gravel build based on the Canyon Grail. Coincidentally (but for the same reasons), China Cycling on Youtube just put out a video of his Waltly build based on the Grail.
The Grail's XS and S sizes run a shorter chainstay (415) and are basically built for a 650B wheel. Currently, I'm riding a 48t single chainring up front with an 11-34 rear cassette. I live in Shanghai, so the steepest climb I face is an overpass, but I can cruise pretty fast if I'm drafting an electric scooter, etc.
Waltly says that given the short chainstay, the max chainring will be a 44t unless I go with a plated design (picture is attached). It costs an extra 70 bucks, though I'm not worried about the money; I'm trying to decide if the aesthetics work and if it's worth it from a speed/gear ratio standpoint. I figured I'd throw it out there. Do you guys have any thoughts?