There's another hidden feature for XmlSpawner that's very helpful: [XmlAdd
This allows you to set up your a profile that contains your individual settings for all new xmlspawners you place. The image below is the XmlAdd window. Once you go through and set any/all defaults you wants, just click Save. You may also set multiple profiles and use the Load option to switch between different default profiles. So you could have default settings for all treasurechests, one for Ilshenar mobs, Dungeon mobs, etc.