Bukkit

You can customize the maximum area per group if you have the mod 'PermissionsEX' or 'bPermissions'.

Here is an example for PermissionsEX.

groups:
    default:
        default: true
        permissions: []
        options:
            maxregionsize: '100'

Here is an example for bPermissions.
groups:
  default:
    permissions: []
    groups: []
    meta:
      maxregionsize: '100'

Any groups that don't have maxregionsize set will default to the configuration option 'limit-amount'.