Except in special cases I generally shouldn't require more than 26 liters for overseas travel. That said, a larger size bag would be more useful for domestic or business travel after I return home. I've been considering getting a Brain Bag, under-packing it, leaving one of the two main compartments empty, and utilizing the compression straps to minimize the size of the bag. This would conceivably keep the bag small and light, but give the bag more versatility after I return home and size/weight is less of an issue.
Are there any ultra-light travelers who've tried this approach or is the Brain Bag still too bulky, awkward or heavy to be considered a good ultra-light travel bag? It appears to sit wider on the shoulders and it doesn't seem as as small or agile as the Synapse 25 or Western Flyer. Do you think the Brain Bag is still a viable bag in this respect, or are the other two bags clearly superior for this kind of light-weight travel?
Also, would the Brain Bag fit underneath an average passenger aircraft seat? It seems a little wide/large for fit under most airline seats. What about the Synapse 25 or Western Flyer?
How does the Brain Bag perform under long-term carry when fully packed?
To give you a little more insight into my thought process evaluating the different Tom Bihn bags:
Aeronaut - Love the duffel-style design but it's much too large for my purposes and doesn't appear to hold it's shape well when underpacked by as much as 50%. Also, it looks a little too much like travel luggage (A little too touristy).
Tri-star - Good size but definitely looks like travel luggage (i.e. touristy) and probably is a little heavy for consistent backpack use.
Western Flyer - Small size reduces versatility and (once again) looks a little too much like travel luggage.
Synapse 25 - Looks like a regular backpack, avoiding the "touristy" appearance, but the small size reduces versatility.
Brain Bag - Looks like a regular backpack and has a good size, giving it more versatility. I'm just not sure how the bag holds up when underpacked and whether it makes sense for ultra-light overseas travel.
PS. I'm one of those who've been waiting for Tom Bihn to release a smaller Aeronaut-style bag, i.e. the "Aeronette". If it landed near the 30-35 liter mark, functioned well when underpacked and didn't look too conspicuous as a travel bag, I would still be very interested in a bag like this.