I found this also. Though I'm not sure entirely how it works ( I just really need to play with it).
http://www.nwnlexico...2_inc_switchesĂ‚Â
How I'm reading this, as long as the OnSpawn has an include for x2_inc_switches then I should be able to add the variable X2_L_SPAWN_USE_STEALTH to 1 (or true) on the creature when it spawn, then it will attempt stealth right away.