What do I need to know about the various bitmap assets in order to create a custom ship art pack?

(I've already replaced the shields and they look rather nifty even if I do say so myself, and you can see the ship inside them more clearly.)

I notice that there are '_mode' bitmaps that seem to be highlight overlays, and some engine overlays, but how are they managed?

How are the different coloured trim lines handled, presumably there's some sort of colour shifting going on within a specific RGB range?

Are the damage decals are applied in sequence with each bitmap divided into blocks of the standard ship bitmap dimensions?

Do the other multi-part bitmaps use similar dimension divisions?

What are the various exact bitmap dimensions?

Any 'protected' RGB ranges?

..?