I have always used Gossamer’ Gear’s ‘Sitlight’ pad as padding and partial load transfer in my GG and Zpacks packs. This new pad beats them hands down for comfort and getting that weight down onto your hips where it belongs. The pad itself (12” x19” x ¾”) weighs 68 grams compared to the ‘Sitlight’ @ 49 grams. Unfortunately the pump weighs 29 grams. The pad is quite difficult to blow up by mouth (but on most trips re-inflation should not be necessary). I am working on plugging the ¼” inflation tube with a ¼” irrigation plug(or similar). I also hope to be able to modify a drinking bottle cap with a 1/4” irrigation fitting and some glue – somethig like my post here: http://www.theultralighthiker.com/sawyer-water-filter/) so I can blow the pad up (if necessary) with my Platypus/Sawyer drinking bottle. The pad can also be used to extend the length of a 3/4 length sleeping pad (eg Thermarest Neo – 230 grams), so the extra 12 grams can be seen as a saving of 98 grams as compared with carrying the Thermarest Neo Xlight Womens which I normally use: http://gossamergear.com/gg-airbeam-pack-frame.html See also: http://www.theultralighthiker.com/ultralight-pack/ & http://www.theultralighthiker.com/hunting-daypack/ & http://www.theultralighthiker.com/the-ideal-pack/
Another great Klymit product is their sub 1kg, sub $200 Grade 2 ready packraft: http://www.theultralighthiker.com/klymit-packraft/
If you don’t own a Gossamer gear pack but want to add an Air beam to another frameless pack for load transfer you could try this idea: http://www.zpacks.com/large_image.shtml?backpacks/options/sleeping_pad_l.jpg
We added this system ourselves with some elastic to a pack with spectacular results, not least being a dry back! Mountain Laurel Designs have a load transfer system (http://www.mountainlaureldesigns.com/shop/product_info.php?cPath=25&products_id=208 using a Klymit pad which goes inside your pack). You could try this anyway if you aren’t handy at sewing. I suspect the idea originated first with Ray Jardine (http://www.rayjardine.com/ray-way/Backpack-Kit/index.htm?g_page=9). I prefer it on the outside of my pack for the dry back option, what a winner! and as a handy trail seat for rest stops.