I run a 32c Gravelking slick on rear of my Wabi classic. It's maxing out the rear brake stay so there's no chance of a caliper there but it's a fixed gear and the front brake is enough. I may go tubeless with which the Adventurer2 rim should work and gain a benefit of some flat prevention on the badly littered streets around here (Albany, NY). The ride is already cushy and smooth and will surely get better with a tubeless pressure drop. I am still running a 28c Gravelking on the front mainly because that size came with the frame. But there's plenty of room and I may bump that one up later. I measure the widths (same make tire on different rims) as 25mm and 32mm. So, for a circle cross-section the 32mm tire would have more than 1.6 times the air volume. And more so, with less pressure the bigger tire will be much more comfortable. Old bones appreciate such!