I'm realizing that with a smaller pack (25L-30L), and stuffing my quilt in a trash bag, I have no need for compression across sides or front. This seemed true last season, using a little pack with basically non-functional side compression, and it seems true with the MYOG pack I finished a month or so ago, with laced side compression as-yet uninstalled.

Just went out for three days with the new pack (30L), and as low volume a base weight as I'm likely to carry (~6# BW, 40* quilt). Had 2.5 days food to start, but could have fit double that (or a bit more). The pack has provision for laced compression system, so I could add it, but didn't miss it at all. By contrast, with my Exos 58, I pull the compression straps as tight as possible.

So at what volume (or change in volume start to finish) do you consider side compression convenient or necessary? Does framed/frameless make a difference?

Compression systems to me make the most sense for backpacks that you want to double as a daypack. 25-30L is not much bigger than most daypacks and at that size a compression system certainly seems pointless. So if I had to throw a number out there at what point it doesn't make sense I would say 30L. I have a GoLite Jam 50L and find the compression system very useful because 50L is too big for most things I do but it gives me the flexibility to have one pack that does it all.

I like compression because it makes my pack look small, even if it does nothing else. It is nice to have a small pack when hitching though. It also seems to add structure to the pack, and that's nice on a frameless pack without a foam pad.

The issue I have with side compression is that all the systems I've seen also constrict the side pockets.

I prefer side compression over front compression because I frequently use the front pocket.

Ideally all exterior pockets would not be compressed or constricted when a compression system is utilized.

I think with side compression, a frameless pack will be more rigid.

As you add more weight, the torso length will reduce less (distance from the top of the shoulder strap to waist belt).

It will allow you to carry more weight comfortably with a frameless pack.

Also, it will put the weight a little closer to your back and things inside your pack will move around less.