I promised an update after the road trip and here it is, a bit belated.
Peter's comments are right on. I already had a locking hitch pin, so with the addition of a set of long hasp Master locks, I was in business. BTW, why do the locks come 3 in a package with only 2 keys?
My first test drive had the bikes bouncing around a little, presumable due to the inevitable bit of play in the hitch receiver. Not problematically so, but there was movement. When I hooked up the trailer, the bikes were absolutely rock solid for the entire trip, both ways. I assume the weight
of the trailer kept the stinger firmly in place. Sometimes gravity does turn out to be your friend.
I was worried about turning and backing up with the bikes back there, but never had even a close call where the bikes came close to the trailer. Might have been a problem if I'd gotten to 90 degrees (because of the little doghouse on the front of the Littlefoot) but I try to avoid that.
The comment about the rubber straps disappearing is well-founded. They're very secure when holding a bike, but when they aren't holding a bike they are loose on the bike mount. I think Donna's idea about Velcro strips is the best solution. I've always got a bunch of those scattered around the house anyway, so I'll throw a couple into the bike rack's storage bag.
Taking the rack off the stinger takes a little practice. If the arms aren't in the right position they can bop one in the head. Found that out the hard way.
Also when taking the rack off, if you have soft hands, it would pay to wear gloves. There's a pretty firm bounce when the spring latch is unlocked that some people would find uncomfortable.
Overall, I'm still pretty pleased. There might be better racks out there, but for the price, it's good value for money.