Well the problem is to carry everything will cause you to be more an issue when shopping. I already carry a large bag with a leg drop for my critical stuff I keep but if I carry the panniers with me things are going to fall somewhere and it really will piss off grocers if you knock over a display with boxes/cans or worst, glass. You're pretty much cut out from many places as most places are narrow aisles unless you're in Wallyworld setting with lots of space. I tend to carry tools, spare clothing, gloves, helmet, repair kit, tire kit, flashlight, backup blinkies, waterbottle, radio, pump, spare tube, first aid, and a few energy bars. I was looking more for something that I can offload my weigh on the bike so when I'm grocery shopping on the way back I can hit all the stores I need to get my supplies then having o double back again and waste a second trip out. Perhaps panniers are not the right thing for me then. I'm looking more for a lockable solution.
Zero_Enigma