Good to hear you have a solution that feels promising. I do like my G-One Speeds.
In case it's still helpful, I've remembered now Thorn's reasoning for recommending tubes in 35c and narrower wheels - still can't remember where I read it but perhaps in the megabrochure.
Anyway, the worry was that a tubeless tyre of this volume was more likely than a bigger volume tyre to deflate fully when punctured, before the leak could be plugged. Since a fully deflated tubeless tyre is unlikely to reseat on the road, you're left with fitting a tube amid a sea of sealant. Putting the sealant inside an inner tube saves on mess.