Just for reference. I fitted dhf 2,5 back and front and there was room left, not much but some.... On my i29 rims they are ~63mm wide compared to the 2,3 which were ~58mm.
You can probably run bigger tyres than we can in Scotland. 2.35 Hans Damp on the back of mine clogs with mud, it's worn the pivots quite a lot. I've had to stop to clear the mud between the tyre and linkage pretty often, not great, especially mid-race. Same size Vigilante has worn the sidewalls more than the frame, but it's much smaller than a 2.35 Mary or Dampf. Same size front Magic Mary is fine, but the back tyre stops me before the front.