Steps:

Add a map.
Create a element.
Set type = Host Group
Show = HOst group elements
Area type = custom size
Set to a hostgroup with 10 hosts or 9 hosts
The algoritm not use entire area... the horizontal space between 2 servers is HUGE and proportional to element size, but is not proportional to number of hosts + size of images.

I attach screenshots of editor and runtime (with tags for betther understand) and XML of MAP + host_group