Thanks Mike, wasn't aware from them, need to browse their offerings tonight!
Art, it sounds like you're using the old Downmat 7, the new one has a better inflation system and the valve is on the bottom of the mat, so no chance of accidentally touching it and opening it.
I'm sleeping comfortable on my NeoAir, which is the same thickness, so I am sure the Downmat should be fine. Also, I find 630 g for a mat which keeps me warm till -17°C lightweight, if I think about the weight to warmth ratio. Its probably also very comfortable, which many UL folks like, therefore why it is popular?!
Anyhow, everyone has different preferences - what works for some, doesn't for others =) I'll see for myself how the Downmat 7 works for me, and maybe I'll experience the same issues as you, who knows.