That Megamat 10 looks awsome. It doesn't pack away small does it? However, it looks cheaper than a downmat 9
Sadly it doesn't pack away small but it's no real problem when strapped across the back of your panniers.
The biggest problem was finding a dry bag long enough to fit the mattress,but Les at Traveldri came to the rescue.
I spent a couple of nights in the lakes at the end of last month,one night it got to -3, I can't give this mattress enough praise,it's warm and I kid you not it's as comfy as my bed.
Steve
I feel a purchase of a megamat coming 
, loads of other great stuff in the box and oddly a box of used Swan Vestas and a used red bag sealing clamp... 

Was it a manufacturing fault, damage, dodgy valve?