I too have the flat bag and I love it.
It does not take much to flip back when fueling and able to carry all kinds of junk in there.
Sunglasses, that is where I throw my gloves when going into the store, garage door opener clipped to the side or in the clear plastic top storage, several earplugs, wallet, phone charger and so on. Sometimes food ends up in there from the grocery store, eggs, bread or other small items.
I think it is ugly as hell, but I love it and it is very functional. Not too big not too small, two thumbs up. It is great, and best of all it came with the bike