I know you all were probably worrying that I wouldn't be able to haul the empty keg in and get the replacement keg home in the new tree feeder, but, you can relax. It worked just fine.
One little adjustment is needed, however. The Mustang has sensors that can tell when someone is sitting in the passengers seat, as opposed to "just hauling grocery's". The 160 pound keg appears to be "people" to the system, so I'll need to actually strap it in with the seatbelt. The seatbelt warning bell went off a dozen times on the short drive home from the liquor store.
All in all, that's not too bad for a first time trial run. Hopefully, in a couple of months when I need to do this again, I'll remember the seatbelt thing...
The funny thing is, I saw that the "passenger airbag is off" light was off and had thought to myself "cool, if I get in a wreck, the airbag will save the keg!". Too bad I didn't add it up.