What pack do you run with your plate carriers?

So folks, here's the dilemma: I've always heard you want to be able to quickly drop a pack if you need to...so mounting directly to a plate carrier or IBA, while done, doesn't seem the wisest choice. The HSP "Flatpack" is cool and all...but doesn't look like it'll sustain more than 24 hrs. Anyone come up with a "better" solution for a 2-3 day pack that wears "well" over body armor? I'm considering lots of options because I'm really tired of slinging my old Condor 3-day over a plate carrier.