[Raapys]

I was thinking; how about manually setting in the coordinates for all hundred systems so that they'll fit with all quadrant sizes?

The smallest quadrant type is 15 systems. That means we'll need a working spiral quadrant with that few stars. So say you set the coordinates for the 3-5 first stars, in a circle of some such, in the middle of the map. Then you start making arms with the remaining 10-12 stars, adding one arm-part for each round, so we end up with a neat little quadrant.

As you get more and more stars, you slowly add to the existing pattern, changing between adding to the core and the arms, making it grow evenly in overall size. Thus it would not be a problem whether the user picks small, medium or large quadrants, because you'll have placed it so that it looks fine regardless of the number of stars.