Second, why am I so hung up on getting as wide a space as possible? Fundamentally, because while ships move outwards in a linear way, stars pile up with the cube of the distance. with the rules we have discussed so far, and technologies where 10-20 milli-Gs (a few cm S^-2) is a lot of acceleration we are talking 3 months or so to transit from one average star to the next - a distance of a couple of parsecs.
So, if 100 parsecs is 50 jumps (optimistic, not a straight line) and for each jump we spend 3 months traversing the system to position for the next jump (reasonable in terms of time, but optimistic because we will have to "stop for gas") that's 150 months or more than 12 years to reach the edge of the map. So I am worrying about nothing, it would seem. Cut it in half - an 8th the number of stars - and you still have 6 years to the edge. And a lot of those systems are going to be junk not worth visiting - we can probably store an adequate amount of information about it in a dozen bytes.
Another note about 100 parsecs - the galactic lens is only about 300 parsecs thick, so the 100 parsec radius would be 2/3rds the thickness of the galaxy!.
My next census will be a 50 parsec radius cube (so still 10^6 cubic parsecs) divided into sectors of radius 10 (so 125 cubes 20 parsecs across) centered on Sirius.