Textures and Performance Settings

How does FL handle textures in relation to performance? If I go into settings and turn down “Texture Detail” or “Object Detail” the textures on vanilla objects become blurry, but with custom ships, it’s really inconsistent.

One fighter seems to go completely invisible except for one texture if the performance settings are turned down. They are all DXT1 DDS textures with mipmaps according to UTF and I can’t see any differences between the way the textures have been saved.

Another ship loses some of its textures on low settings, but the parts that lose the textures just go grey and untextured rather than invisible. Most custom starspheres do this on low settings too.

Another thing I’ve tried is changing the format. I did get textures to show up on low settings instead of going grey/invisible, but there’s no change in resolution (which defeats the purpose, since there’s no difference between high and low settings.)

I was thinking it had something to do with LOD ranges and mipmaps, but so far I haven’t found something that works like vanilla models.