The venerable Greenfield kickstand on my Tour Easy doesn’t quite match the mounting plate under the frame, with the result that it can pivot just enough to make the bike tippy with a moderate load in the rear panniers. I’ve carried a small block to compensate for sloping ground, but I finally got around to fixing the real problem.
The solution turned out to be a spacer plate that fills the gap between the back of the kickstand casting and the transverse block brazed to the mounting plate:

That little lip is 2 mm wide, so it’s not off by much.
The aluminum came from a Z-shaped post that contributed its legs to a previous project. I flycut the stub of one leg flush with the surface, then flycut a slot 2 mm from the edge:

For no reason whatsoever, the width of that slot turned out exactly right.
Bandsaw along the left edge of the slot, bandsaw the plate to length, square the sides, break the edges, mark the actual location of the mounting plate hole, drill, and it’s done!
An identical Greenfield kickstand on Mary’s identical (albeit smaller) Tour Easy (the bikes have consecutive serial numbers) fits perfectly, so I think this is a classic case of tolerance mismatch.