A well tool can include a downhole anchor with at least one outwardly extendable slip including longitudinally spaced apart grip structures, and a longitudinally extending beam which connects the grip structures to each other. The beam has a radial thickness which is greater than a lateral width of the beam. A slip retainer retains the slip, and a spring inwardly biases the slip relative to the slip retainer. The spring surrounds the slip and the slip retainer. An area moment of inertia of the beam with respect to a lateral axis through a centroid of the beam is greater than an area moment of inertia of the beam with respect to a radial axis through the centroid of the beam.