You can get a full shelter i.e. tent, sleeping bag and mat for just over 4lbs. It is expensive though.

PHDesigns Minim 400 Down Bag @ 670gms Good to -5C.

http://www.phdesigns.co.uk/product_info.php?cPath=25_58&products_id=118

Thermarest NeoAir Sleeping Mat (medium) @ 370gms

http://www.thermarest.com/product_detail.aspx?pID=134&cID=1

TerraNova LaserLight Competetion tent @ 940gms

http://www.terra-nova.co.uk/Product_Type...iew=description

Total 1.98 Kg = 4.356lbs

Or you could just forget the LaserLight tent and add 200gms to the PHDesigns Minim down bag with a Goretex shell and add a silnylon tarp Intergral Designs Silshelter @ 470gms

http://www.integraldesigns.com/product_detail.cfm?id=729

Total 1.71Kg = 3.76 lbs