Right, sorry for the massive delay, work has been crazy busy,
here's the rear with a Conti Speedking 29x2.0, 50mm at its widest on Halo 29er (23mm internal) rims
loads of room there
this is an Onza Ibex 2.4 (its huge) 58mm wide on the same rim
fits ok, bit tight down at the chainstays
the only other tyre I had to try was a Conti Mountain King 2.2 (56mm on the same rim) but its much smaller than the Onza