Okay, so I did the calculations for the size and shape of Vathari space last night. My end result was this:
157 total colonies, discounting important worlds (Vathar, Oncar).
20 major colonies, also discounting said worlds.
Diameter of Vathari space: 774.375 lightyears.
Twenty sectors, one for each major system, each with a sphere of territory about 203.65 lightyears in diameter, with approximately 7.85 colonized systems distributed in each sphere.
From there I estimated my FTL speed to be 11.26 lightyears per day, or about 4110.5c.
Now, of course, I am wondering how this stacks up against everyone else's estimates. I am of course doing this more for fun than game reasons and in the game itself I will probably adjust to what seems reasonable.