Ultraspire Fastpack

I assume you're looking into this with fastpacking in mind rather than SUL backpacking. If SUL is your goal, then I'd suggest something like the MLD burn, Zpacks Zero, or Gossamer Gear Murmur.

For fastpacking, a few items/techniques that come to mind:
With 1000 cubic inches bring as little as you can get away with and make sure your biggest items are as compact as you can make them.

Potentially large items:

Sleeping Bag/quilt–a quilt will save you significant space over a sleeping bag. Assuming you'll be spending most of your time moving, not hanging around camp, I'd skip on a puffy jacket. Use a slightly warmer quilt (since you'll probably be pretty depleted by bed time) or just get out your head lamp and start moving when it really gets cold in the pre-dawn

Tarp–use a small cuben tarp like a zpacks hexamid solo + or flat tarp. If you're not using trekking poles, zpacks superlight carbon poles for the hexamid

Sleeping Pad–I'd recommend something super light, compact and comfortable like a neo-air xlite short. Some people would use closed cell phone like a gossamer gear nightlight, but I sort of doubt that something like that would fit well into a pack like this. Almost better to avoid using a hard frame since the pack will hug your body better with soft stuff. If its a small/light enough load transferring weight to your hips matters less than evenly wrapping the weight around your body. I prefer to have weight clinging to my upper body when I'm running than restricting my hips, but thats me.

Food/Kitchen–either bring a tiny cat can/titanium mug setup, or better, go stoveless. Bring the most energy dense food you can find & limit yourself to 1.5 lbs per day. There's significant weight/space savings here. Look for foods around 140 cals/oz & higher–almonds, peanutbutter, banana chips, sunflower seeds, choc covered esspresso beans and crushed kettle chips and sweet potato chips are some of my favs. A few days food doesn't have to take up much space or weight if you make sure to check nutritional labels for cals/oz in the grocery store. Most energy bars aren't even that efficient.

A minimalist rain jacket like the North Face Triumph anorak, OR Helium II or Rab Pulse are good bets.

If you think you're in should season conditions or above treeline in cold windy conditions, a breathable windshirt with a little bit of insulation value could serve as a nice second layer. A rab boreas or marmot ether driclime would be good here. Or you could just go with a super light windshirt

Also, if you're fastpacking in an area with a decent amount of water skip the water bottle system on the spire and just wrap an evernew blatter around a squeeze filter, and camel up at water sources. Your back will be much happier, and you can put other items like your shell and tarp in the bottle holsters.

I'll be in the market for a fastpack next year, but I think I'm going to try this vestpack that was designed for speed alpinism (derived from a pre-established running pack design) : http://gearjunkie.com/best-in-show-outdoor-retailer-2012

Hope thats helpful! Been brainstorming about this myself.

Serge, do you own one? My questions is intended for those that actually use one with what gear they are using. I already generally have an idea of what I don't already have and need to make or purchase. For instance, my myog pack weighs in at 8.5 oz. which isn't bad at all but not intended for fast-packing/trail running trips.

I had one and lost it earlier this summer. I could never get the fit right and it rode worse than my Deuter Speedlite 20. The bottles are nice but the lids fit poorly. The 20 ounce Ultraspire bottles have the same issue.

I intended the pack for over ambitious Nolan's 14 scouting trips. I wanted to be comfortable if I needed to wait out a thunderstorm or camp for the night. The Fastpack easily carries more than the Speedlite 20. Here's what I carried

* 1.5 Days of Food/Snacks/Dog Treats/Salt Pills
* Patagonia M10 W Jacket
* Patagonia Nano Puffy W Hoodie
* GoLite Wisp Rain Pants
* GoLite 2012 Poncho Tarp + 6 Stakes + Guylines
* SOL Escape Bivy
* BD Icon Headlamp
* Gloves
* Spot
* P&S Camera
* Steripen
* GPS
* BD Ultra Z-Poles
* Small First Aid Kit (including chemical handwarmers, fire starter, lighter)
* L/S Shirt
* 26 Ounce Bottles (2)
* Maps
* Compass
* Medium Size Dog Coat(I think)

When it came to buy another day pack, I repurchased the Deuter. Not only does it ride better on me, it has straps for snowshoes or skies.

This fall, I won a Ultimate Direction Grind 16 (http://www.ultimatedirection.com/p-589-grind-16.aspx?category=hydration-packs). I like it a lot. It rides close to my body without any shifting or rubbing. Fantastic!

Don't own the pack. You're question related to volume, so I thought I'd try to be helpful. I tried the pack on too, and it felt too small for my 6'1" frame.