Originally Posted by
merlinextraligh
If that bag is on a high end aero bike with expensive aero wheels, it doesn’t make much sense to carry your stuff there. Without wind tunnel,testing, I’d bet you dollars to donuts it’s way more efficient to carry your stuff in an appropriately sized set bag, which can be anywhere from a micro wedge to an ortlieb bag that carries 15 liters.
Heck, a decent sized Bag on top of the top tube behind the steerer tube,, or a even a frame bag would be more aero.
It's all still pointless speculation until we know who these riders are and what they're doing. I'd absolutely ride an aero bike with full gear for commuting, and then a big bag for a change of clothes.