What do folks think of this idea for cold temp operation. These are 2.5" X 3" and work for up to 10 hours. If we had a holder for the outside sides of the battery cage that accepted a handwarmer slid in and kept secure it would help keep things in battery land cozy, even among battery swaps. Need to have a solid outside side wall and probably a mesh inner wall to let heat into the battery compartment but keep the cold out. Especially in light of the 1.6FW update this might be a great way to make sure you aren't performance limited at a critical moment. Thoughts?