I've killed modded Ct's just by having the torque of the exhaust wheel try to spin the larger comp wheel. The problem is that the Ct shaft is not constant diameter, and when it steps down to go through the thrust collar, it is a sharp machined cut, not a radius. That creates a week spot, and when that efficient (yes the Ct turbine is efficient) turbine whips the shaft around, the lazy compressor wheel will have nothing to do with it. It looks like you clipped the turbine wheel, which is a good thing for longevity. You lose a lot of low end efficiency by clipping, and that equals a direct reduction in the twisting force that the turbine can put on the shaft, basically it makes it so that the turbine can't over stress the shaft as easily. I'm pretty sure that the major reason people clip exhaust wheels is to prevent shaft failure, it just so happens that it also increases top end potential. That, teamed with your ball bearing center housing should really help with the life of that turbo.
-Would you mind snapping a shot down the oil hole so I can see into the bearing case?
