ICPD quest question (possible spoilers)

[DC]

Hi, really enjoying the game so far!  I'm completely stuck on the ICPD quest and wondering if someone will take pity, I killed the agent who stole the ICPD thing, he said that he was robbed, he didn't know where, but that he passed some sloped roofs (I think...?)

I see from other forum posts that I should be looking for Duff's gang, but I've been through every room I can find on this level and haven't found him anywhere.  I've killed three groups of Gangsters, is he related to those?  Should I be looking on some other level maybe?  Most other quests have had some sort of clue as to where to look, maybe I missed something, I'm totally baffled though, would love to to just know where he is and move on at this point...

Thanks!

[Grim]

He said there were a guy and three girls in the gang. Look for Duff and three named girls in the drop zone.
For info, drop zone has several "levels" accessed through ladders. If my memory serves me well, there is one near the guards at North. Search on the upper "level" from there.

[Pipboy]

From harcore city bar back entrance to the east, there is the tall slanted roof and duff if i remember correctly

[DC]

Ah, thanks!  I assumed it would be on the same level, I guess the dropzone extends the height of Core City?  Anyway, thanks for the pointer, thought I was going nuts...