A safety valve for use in a subterranean well can include a housing assembly having a flow passage extending longitudinally through the housing assembly. An outer diameter of the housing assembly is eccentric relative to the flow passage. A well tool can include a magnetic coupling between magnet devices. One magnet device includes a series of magnets which are unequally spaced circumferentially about the other magnet device. Another safety valve can include a longitudinally extending flow passage, a closure device which selectively permits and prevents flow through the flow passage, and an outer diameter which is eccentric relative to the flow passage.