> But 99% of that latency in the above 490ms figure is the extreme distance of the satellite, and not whether or not one site is slightly further down the sphere, as viewed from a theoretical observer sitting on the satellite.

Path length varies from ~34500km to ~42000km (~115ms to ~140ms). So, assuming an ideally placed teleport, from 115 * 4 = 460ms to 115 * 2 + 140 * 2 = 510ms speed of light delay on round trips. This is why I said I found 492ms to be an amazingly over-precise number. Just call it 500ms. :P