...at least, that is what I would like to say I did. Unfortunately, I forgot about the empty laptop pocket, tried to cram my hoodie into the main compartment, and couldn't zip the bag closed. So I went with a bigger bag. But I totally could have done it if it wasn't for you meddling k....I mean, if I hadn't forgotten about the laptop compartment! I ended up using a 26L SwissGear Weekender bag, which was fine. The bag is nothing to write home about, and really doesn't feel like twice the size of the Kanken, though. You can see my packing list here. This was for a trip to Indianapolis for GenCon, which I think is the biggest board game conventions in the US (don't quote me on that). Even though it was Indianapolis in August, I knew we would mostly be indoors, so I brought two pairs of pants and only one pair of shorts (I run cold, which also explains the hoodie for a trip in August...).
I brought 4 shirts (I was wearing one). Two were a wool blend that I wore twice on the trip. Wool is amazing. It doesn't smell. I've exercised in the same shirt for 5 days, and you can barely tell. I could have just brought two wool shirts and just alternated them (all I was doing was playing board games all day...), but I wanted some variety, and I had the space. Also, I still worry that people will notice I am wearing the same clothes over again and think I am weird, especially after the 3rd or 4th time...
I would like to carry fewer toiletries and liquids, but I have rosacea and until I get it somewhat under control, then I am going to be bringing a lot of liquids. Next time, though, I am going to decant them into smaller tubes like these from Amazon. I am also prone to migraines, so I usually have a ton of aleve on me (those little blue pills in the small bags), an eye mask, and anti-nausea stuff (ginger chews and pepto tablets).
Except for the hoodie in the laptop compartment, I wouldn't really have done much different. I was actually amazed that I basically got a week's worth of stuff in the Kanken. I did only use the headphones on the flight back, but I was glad I had them. As I said above, next time I will decant my liquids for a short trip like this, but it is good to know that I do actually have the room to pack the full sized bottles for a longer trip.