I think you have the "sweet-spot" combo, looks great! You'll love towing the expressway and not even feeling semi's passing due to the PP and superior aerodynamics of the Airstream and GC.
I have a similar rig (25 foot Safari @6300lb GVWR, 2011 Chevy Traverse 6400 lbs, 3.6L 6-spd). I tow with a Hensley and Direclink controller...an excellent match with the high-speed and low-speed settings. I did downsize the tires to help keep the tranny in 5th while cruising on the highway, but otherwise it tows like the wind and handles really well. I expect you'll be as pleased as I am.
Gary & Debbie
2001 Safari 25 SS
2011 Chevy Traverse 3.6L AWD • Hensley • DirecLink • McKesh
Set-up by Can-Am RV