The 26" height really only works if you check the bag. Otherwise, it doesn't fit anywhere.

I'm not a fan of expanding bags (eg, unzip to get more room); overstuffing ends up being hard on zippers and the bag, and they never fit. I use both the side pouches on my bag, because I always travel with a full eight days of clothes; on airplanes like the A321, the bag won't roll up on its side because it's not quite skinny enough, and there are some airplanes that have narrow enough overhead bin doors that the bag doesn't want to slide through, the skinny way, without assistance. On anything regional, of course, it just gets gate checked.

If you do 2 day trips and pack accordingly, it will probably go just about anywhere. I always plan for extended time and an inability to get to a laundry machine, so I need to be able to get to the next full rest day plus one more, to be safe, plus what I'm wearing, so eight days. Even with everything packed tight and rolled, it's still a little bulk. I've never felt a need to expand beyond the existing size of the case, though (meaning using an expansion feature). As the case is now, it fits under certain cockpit seats, and in most overheads, so I wouldn't want to go any thicker.