I've been using an Exped 7 DAM for years now... home & trail.
I have a Stephens "Warmlite" too, but I prefer the Exped.
But you are right in that the inflated mat keeps the down from being compressed. Works great!
The only issue with using the DAM as your only under insulation is that the colder it gets, the more noticeable it will be when your shoulders, hips, etc press against the side of the hammock, compressing your top quilt.
But some use the Exped 9 which is even wider than the Exped 7 I use.
don`t leave the CREATOR out of the creation!