I like it a lot. Very handy for cutting larger panels, simple and elegant solution. I'm wondering if this could be adapted to using a recessed drawer slide. That would move real easy back and forth. But I'm not sure how well thumb screws would work on that.
Anyway, great idea for my next crosscut sled! Let's see, I need replaceable ZCIs, clear plastic shield, fence guard, groove for sawdust, T-track for stop blocks, and now an extensible stop block....