I have been looking for a replacement for my over sized seat bag with the addition of the back rack because it interferes with my trunk bag (see above), which I also want to replace at some point. I have been looking online for quite some time but nothing really stood out except for the Banjo Brothers Waterproof Saddle trunk but that thing is huge and would also interfere with a trunk bag, too. Then I found some pictures of their barrel bag that looked kind of enticing since it also can work on the front of the bike which is something I have also been looking for my Bianchi San Jose.
Just about everything I saw online were with Brooks Saddles and since I owned one I thought it might be time move the Cambium back to the Randomuter since it's finally starting to feel broken in. The straps for the Barrel Bag are a perfect fit for the Brooks because the saddle has strap holes on the back. The Barrel Bag also has good blinky holder, another one of my prerequisites, along with enough volume to hold riding jacket, extra gloves, and my first aid kit.
Unlike other bags that would attach to the seat post the Barrel Bag has an elastic strap that can attach to the seat post or frame to prevent swaying. Sitting on the bike it seemed like the back of my thighs might just hit the sides the edges of the bag. That is something that I will have to test out when I go for a test ride.
I also attached my old Army Butt Pack to the rear rack as another pannier. I found it in my old Army trunk in the attic and thought that this would hold my lunch bag perfectly. It mounted to the rack nicely but I will have to find some small snap links for the top of the rack if I want to make it more removable. Since the butt pack seems to work fine, I probably don't need a another trunk bag. A test ride is what is needed now.