Thanks for posting that, Dave, neat trick.
My only concern is, that if my chain saw is so dull that it needs more than a touch up, it's gonna be tough to do all that cutting that making that stump-clamp requires.
Like Windy, I don't sharpen outdoors.
Back as a teenager, when I had summer jobs doing seasonal dock building, I learned that whenever we went into the woods to cut dock poles, it's easier to carry already sharpened spare chains in a Tupperware bucket, soaked with bar oil. Then, if a chain got dulled by cutting too close to the ground, a clean, sharp chain can be put on.
The dulled chain, which often has dirt grit in it that contributed to the dulling, went into a plastic bag to be flushed clean and re-sharpened back at the shop. My boss insisted we do that, because it was faster to get back to cutting, and better for the saw instead of running that gritty chain over the bar and sprockets.