We live in a Streng with single pane, 2-panel 10 foot sliding patio doors to the back yard. For energy saving purposes, we'd like to upgrade to double pane, maybe Milgard, maybe Blomberg; we don't want to break up the space into 3 or 4 panels-we want to keep the open look of the 2 panels. We know the new doors would be really heavy. Has anyone out there done this, and if so, how well does your 5-foot movable panel on the slider actually work? Any recommendations?