I was running rigid steel singlespeed in a 24hr (4x) and want some cush so put a Tioga DH tyre on the front of the VERY cheap wheel. Back then I didn't understand anything about Crr or tyre sidewalls, etc so it was probably worse than just fitting a skinny XC tyre.
People ran 2.5"+ on 17mm internal on MTBs for years. It'll be fine.