In reply to Guy Hurst: Exactly what I did.
Neoair Short combined with a cut down Multimat. Velcrowed together to make full length mat. But if Neoair deflates I have the Multimat that can be used for torso and legs into the rucksack.
This method also packs well into a 35L OMM Rucksack as the Multimat is used to line the Rucksack and give it support.
Overnight wild camp in 35L sack total weight 11kg inc food.
Couple of photo's of the rucksack but not the Multimat
https://plus.google.com/photos/117542672402472670569/albums/546789033088563...
I did that 30 mile walk in Trainers to keep the weight down