If it seems that no matter what you do with rvmat or model settings the HDR lighting will always go nuts inside the vehicle interior, outside the model things are fine and it looks just like every other model but inside the lighting makes everything slowly brighter until the whole interior is white or grey with some spots of green here and there.
Then you should add these config values.
viewXXXShadowDiff = NN; viewXXXShadowAmb = NN;
For example the BIS M113 has them like this:
// let only small amount of direct light go through, to avoid shadow artifacts viewCargoShadowDiff = 0.05; // reduce amount of ambient light as well viewCargoShadowAmb = 0.5;
That should fix your bad interior lighting.