[MDL ED] Book Cases

[Rapture]

I don't think your map size is to large (Sure the loading time might varyingly be longer or shorter on different comps.) right now. If you have (I think 6 floors), you will only reach 3-4mb in size when your done.
If your gonna go with Decals, try using what is available in the "static_objects>decals" section first.

The actual decals (That apply to any surface) really bloat your map size and I only use those for special cases and very sparingly.

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To elaborate on what The Chaser said, select the objects you want. And click "B" to make them into a compound.