For those who don’t sew – or who don’t need to sew: You can use these wonderful little Clam Cleat Lineloks and some eg 2mm Spectra/Dyneema to lash your excess gear to your pack. I always use these lineloks on my tents and tarps: http://www.theultralighthiker.com/the-perfect-guy-line-for-a-hiking-tenttarp/
Here is my Klymit pack raft (http://www.theultralighthiker.com/klymit-packraft/) attached to my Zpacks Blast (Zero http://www.zpacks.com/backpacks/zero.shtml) @ 200 gram pack. You can see I have three tie downs. I should have tightened them up a bit more and bent the raft down at the sides (or rolled it up shorter), but you get the idea: you can lash an extra bag (eg http://www.theultralighthiker.com/a-tardis-folding-space/) on top of your pack for an expenditure of approx 7 grams!
Here’s how to rig them:
Clam Cleats are available here in eg packs of 100 http://www.cleats.co.uk/browse-by-product/line-lok-guy-runners/cl266-mini-line-lokr-for-1-3mm-lines.html Also available locally (Oz – and quickly) here: http://www.tiergear.com.au/11/online-shop/clamcleat-cl266-mini-line-loks I find the Glow-in-the-Dark best. I always use the reflective line for guys etc too, eg: http://www.tiergear.com.au/11/online-shop/reflective-glowire-15metres The Clam Cleats are made by these folk: http://www.clamcleat.com/products/cleats-for-1-6mm-rope/cleats-rigged-on-a-rope-24.html who have some other interesting stuff.