Try searching the forums for "GraphicsConfiguration.xml" or "GraphicsConfigurationOverride.xml".
On a related note, I was trying to completely disable shadows for testing purposes and could not, but I did manage to knock out everything except the cockpit shadows and make them look comically bad, which might actually be useful for you.
Try pasting this over the contents of your "GraphicsConfigurationOverride.xml":
XML:
<?xml version="1.0" encoding="UTF-8" ?>
<GraphicsConfig>
<SpotShadows_Low>
<NumCacheShadows>0</NumCacheShadows>
<NumSpotShadows>0</NumSpotShadows>
<CacheShadowAtlasSize>512</CacheShadowAtlasSize>
<CacheShadowSize>128</CacheShadowSize>
<SpotFilterQuality>0</SpotFilterQuality>
</SpotShadows_Low>
<Shadows_Low>
<Profile_General>
<SliceSize>512</SliceSize>
<NumFrustums>0</NumFrustums>
<FilterQuality>0</FilterQuality>
<FrustumCockpit>
<DepthBias>0.0001</DepthBias>
<DepthSlopeBias>5.0</DepthSlopeBias>
</FrustumCockpit>
</Profile_General>
<Profile_PlanetApproach>
<SliceSize>512</SliceSize>
<NumFrustums>0</NumFrustums>
<FilterQuality>0</FilterQuality>
<FrustumCockpit>
<DepthBias>0.0001</DepthBias>
<DepthSlopeBias>5.0</DepthSlopeBias>
</FrustumCockpit>
</Profile_PlanetApproach>
<Profile_PlanetSurface>
<SliceSize>512</SliceSize>
<NumFrustums>0</NumFrustums>
<FilterQuality>0</FilterQuality>
<FrustumZeroCanBeOverridden>1</FrustumZeroCanBeOverridden>
<FrustumCockpit>
<DepthBias>0.0001</DepthBias>
<DepthSlopeBias>5.0</DepthSlopeBias>
</FrustumCockpit>
</Profile_PlanetSurface>
<Profile_StationInterior>
<SliceSize>512</SliceSize>
<NumFrustums>0</NumFrustums>
<FilterQuality>0</FilterQuality>
<FrustumCockpit>
<DepthBias>0.0001</DepthBias>
<DepthSlopeBias>5.0</DepthSlopeBias>
</FrustumCockpit>
</Profile_StationInterior>
<Profile_AsteroidField>
<SliceSize>512</SliceSize>
<NumFrustums>0</NumFrustums>
<FilterQuality>0</FilterQuality>
<FrustumCockpit>
<DepthBias>0.0001</DepthBias>
<DepthSlopeBias>5.0</DepthSlopeBias>
</FrustumCockpit>
</Profile_AsteroidField>
</Shadows_Low>
</GraphicsConfig>
Make sure shadows are set to low and see if that improves anything, performance wise.