I use the Smart Parts loop pack. Easy to get the pots out, then the loops for the outer 4 pots spring back between the 5 inner pots for a lower profile. More flexible than some other packs out there.
Oh, & I find it supports my lower back really well
I use the Extreme Rage 5+4 pack with good results, and just got a Jacko pack with some loops added which seems promising. I recommend also Mpack packs, which can be viewed at www.topstitch.net. (Only reason I didn't just buy one was because I got the Jacko for $30.)