This is excellent! Thanks!
As it happens, I do want to trim the ends of the part, but not the sides, and I can get that by setting a non-zero offset on the ends.
This is the second time I’ve been caught by KM’s clipping action being calculated against the center of the toolpath, rather than against the cutting edge. (First time was last week, when I had mistakenly set “Inside only” on the contouring pass of my curved piece.) It really feels wrong to use the center line for clipping – in this case, anything less than a stock offset of .125001 will suppress the cut on those ends entirely. (I’m sure it’s much easier to stick to the center line, but it does yield surprises.)