AI effects mdl and contact points

Hi,I wonder what the rule is for AI craft to show the effects.Does it depend on the contact points that trigger certain effects? Or does it depend on the MDL?Fact is that I am converting the HAMA FS2K2 Congou into an AI vessel (I do have the FS2K4 AI version as well but it doesn't work as it should in FS2K2).I first tried the FS2K4 AI but it bounced and disappeared. Then I replaced the air.file by the Marignan.air and it worked. But no effects whatsoever.I then used the FS2K2 Kongou mdl and it worked fine again and now the flag is showing as well. But still no wake or spray effect.Holger in his AI_ships readme told it was something to do with the contact points. And indeed, the contact points of the pilotable version are different from the AI version.But what triggers what??? And how do you find out?Roby