I’m running the Ibis 941 rims, 41mm external and 35 mm internal and love them. Tyres plump up nice and big, currently on Bontrager 2.4s but have used Minions 2.5WT, Ardent 2.4 and nobby Nicks 2.35s. Really nice thing about the width is running lower pressures, 17-19 psi in the front and 20-22psi in the rear so always loads of traction. For Info I ride in mid-Wales so Nant-yr-arian, ClimachX and Coedy with plenty of off-piste stuff in Dyfi and mid-Wales generally. Not had a bad experience with them, even when the I put a hole in the rear (unfortunate rock strike) I didn’t even think once about going smaller. Luckily Ibis sorted it out as a crash replacement so didn’t have to pay full whack, but I would of.