yea, I really like the circular map too, but it looks ugly with so many hosts just like mine did.
I see no choice. Even if you did change the code to force 2 pixels between each icon, what you would end up with, is a circle the size of the room you are sitting in (ok, maybe not quite that big).
So, use nagiosmap to layout the network in a pretty circle also and you will see, that a circle just isn't going to cut it. It's going to be too big with a huge empty hole in the middle with nothing in it.
Warning:now that you have so many hosts, nagiosmap is going to first start out with no coordinates at all. It will look like a ball of fishing line all tangled up, and you have to pull, push, and play with it for an hour or more to untangle it. Save often..... I actually found it theraputical and kinda fun.