aha!
turns out the solution is not in krandr but in the monitor kde settings. wherein one may drag one monitor atop the other, establish which is the primary, and so on. now, according to krandr, i am running a monitor at 1920x2280. which is pretty cool, though the moon on my desktop is now enormous and cut in two. but, hey, if that's the worst that ever happens . . .
which i report in case it's of use to anybody else. i personally think it is tremendously cool.