Had the same experience in RES. Have some Engineer stuff with me but wanted to do the BH CG only to realize that it's impossible to survive in a RES carrying Engineer stuff no matter how many they are. All i could see was red dots on my scanner, at some point i think about 8 - 10 ships were shooting at me. Good thing the Anaconda (which i use mostly for hauling stuff and the one im modding) has good enough shields and hull to let me low wake away.
No different to any other cargo excluding limpets. I mean, you fly into a specific instance which is there purely to spawn npc pirates with cargo in your hold and are then surprised that they try to kill you? It's not Farmerama.