I recently bought that exact pulley (the little red CMI) for lighter rigging, as I figured it would be much handier to move around in the tree.
We damaged it in the first tree we put it in. We were using it to carry speedline drops out of a locust tree for some of the heavier branches because we did not want to heat up the rope or 'biners with non-rolling friction on some of the larger branches. Attached to a loopie with a steel carabiner, the bends in the side plates straightened out and pinched the pulley. It was sliding down the speedline without rolling. The cheek plates were squeezed tight against the sheave.
Nothing we cut was more than 750 lbs, and the speedline was rigged pretty loose and stretchy to soften the blow. I was really disappointed that it quit working right, especially since the pulley had a higher rating than the loopies or the carabiner. They never seemed to even get nervous by the loading, but the pulley got damaged "out of service".
It's a nice little pulley, and I am sure it will not fail until the rated load. It will quit working correctly quite a bit sooner than 7k it is rated at.
We fixed it by taking it apart, hammering out the cheek plates, and replacing the axle with a grade 8 shoulder bolt. Lubed it, and it is back in service (light duty, of course).