I emailed harken about the sheave loads, and here's what they gave me:
> Halyard sheave blocks are going to see a little more load because they turn at a greater angle. I would think the spinnaker halyard sheave would see just under and the jib halyard just over 1,000 pounds maximum working load.
It is really a non issue, though, because as far as I can find, rig-rite is the only place selling replacement sheaves that'll fit my jib-box. They need to be 31/64" wide...
