I'm still on vacation (until tomorrow) but it's raining, so let me update y'all on the luggage carrier. In short, it's working great. It has a bit of play where it slides into the receiver, which lets it rock from side to side just a bit. I got some cedar shims to wedge in there, but there's not even enough room for that. If I end up using it again, I'll probably drill and tap the receiver for some bolts to wedge it tight.
Yeah, it does sit pretty low. It scraped a couple times on entrance ways into gas stations and whatnot. It should be goosenecked up a couple inches.
With the extra weight back there, it does affect the handling. The tail tends to wag the dog, so to speak. But it's not too bad. Not any worse than a trailer would be, I suspect. And the convenience of having everything down low is great. I unloaded and had the thing removed from the car in about four minutes, ready to maneuver around town.
The aerodynamic benefit is undeniable. I'm getting the same mileage with it installed as with it off at highway speeds. I definitely couldn't say that when I had the bag strapped to the roof rack!