Methinks that within the limitation of frameless packs -- the weight at which a particular frameless pack starts to collapse depends almost entirely on what "frame" YOU insert into the pack, how YOU pack your gear, and how well the pack cinches down into one tight bundle -- either when full or less than full.

In other words, most all framelss packs "start out" basically the same (one large sack) -- and the important aspects that differentiate one from another in the comfort department are:

1. Shoulder straps -- how comfy are they to you (i.e. material, padding, curvature and size). For example, many love Gossamer Gear frameless packs but their wide shoulder straps make them uncomfortable for me.

2. Sizing -- important if the pack comes with a hip belt

3. Cinching -- are the straps well-designed for cinching down the load?

Once you pick a frameless that meets the criteria above, it's a matter of inserting an appropriate frame, and packing carefully to minimize any discomfort and imbalance. Using an "extreme" example to illustrate a point, if you've got a good load but choose to use an ultrathin, spongy soft Thinlight pad as your "frame" -- then it's hardly the pack's fault when it collapses at well below 30 pounds. In contrast, inserting a sturdier frame -- such as blue foam pad -- or at least a self-inflating pad -- will make all the difference.

Given the nature of frameless packs and all the above -- I find it odd that one can form a straight conclusion that one particular pack will collapse at a lighter weight than another.