The Evo platform is designed to adjust from a 24" frame height to a 28" frame height. The reason is that the taller frame is more capable of providing shoulder lift at really heavy loads, while the 24" frame is much more nimble at getting through brush.
The Unaweep is designed to marry the two and use a 26" frame. We have tested this frame height extensively, and feel that it is a great size for most uses.
The Unaweep bag will work on a 24", 26", or 28" frame, but is optimized for the 26". A set of 2" frame extensions is all that will be needed to take a standard frame to the Unaweep height.
