SplinterGroup commented about 11 hours ago Really great mods Ross. Looks like you just release, then slide it up to your workpiece with a small gap, lock down and clamp. No need for excessive travel!
First thing I though of with the split piece was to cross drill and epoxy in a pin. I'll usually snip of the threaded portion of a long machine screw for pinning since the threads really give a great bond
Splinter - Yes, I can just snug it up so the pad is flush to the workpiece, tighten the knob to hold the clamp body in place, and rotate the cam lever a bit to tighten it fully. It doesn't have to move very much at all to get a firm grip.
I didn't think about repairing the plunger crack like you've described. That sounds like the machine screw would both clamp the split sides together as well as add rigidity.
