I'm looking for an Exped solution to a simple problem. I carry my multi-mat and down mat 9 dlx [LW] strapped to the back of my Osprey backpack. On my last outing I rolled the two together, each folded in half (width), and the down mat rolled inside of the multi-mat. This made for a fairly compact roll, with the added benefit of protecting the down mat. Unfortunately I didn't have a suitable storage bag for this combo and used an [insert another brand name here] stuff sack. I'd like to carry on with this method of carrying the mats however I'd like to have a proper, suitable storage bag. I believe your waterproof compression bags would suit, however I'm not sure if I'd need a medium or large for this application. I thought perhaps you could use your available products, and do a live trial to determine which of the compression bags will suit my desired configuration.
On a side not, I'm not sure if you are aware of this. Your 20L shrink bags, which I am a huge fan of, fit perfectly inside of the Osprey Argon backpacks. The pack main compartment horizontal cross section is almost exactly the same as the shrink bags foot print. This is awesome for me as Osprey and Exped are my two favorite manufacturers.
Looking forward to hearing back about the waterproof compression bag trial.