I tested this strange phenomena, and it seems that ModuleCargoPart has to come before ModuleInventoryPart to make this work. So I hacked some extra lines into the mod to make it output in this order for all the instances containing just ModuleInventoryPart instead of ignoring them... Only to find out after I finished writing that ModuleManager has this nifty little trick that lets you index the order of how MM does the edits.
@PART[*]:HAS[@MODULE[ModuleInventoryPart],!MODULE[ModuleCargoPart],!MODULE[KerbalEVA]]:FINAL
{
MODULE,0
{
name = ModuleCargoPart
packedVolume = -1
}
}
This little hack works like charm for me (unless, on an unrelated note, I have NodeHelper installed which causes EVA Construction to throw whenever I try to detach a part). If it works for you I might throw it in a nice package and shoot it up to the dock.