Did you drag the .pkg inside the .dmg into Casper admin? And as a bonus, select 'Install on boot drive after imaging'? Dragging the .dmg alone will not work.
This is what works for me.
Dumb question, but how do I view the contents of the dmg? I don't see a show package contents when I right click the dmg, and double clicking goes straight to the installer screen.
--edit, I selected Open using flat package editor. There's about 30 packages in there, which one do I need?
@brandobot
Just double click on the .dmg, you don't need a package editor since OS X will open it just fine.
.dmg by itself:

Double clicking on the .dmg

Drag that nice Office Folder pkg into Casper Admin
Thanks. I feel so stupid. I already removed the package from the dmg... lol. That's why it was trying to install when I was double clicking.
@brandobot
No problem! Just mark this discussion as "Solved"!