FWIW, I have the exact Curt hitch on my 2012. When you install it, make sure you super tighten the driver side bolts so that there is absolutely zero "play" between the hitch, the underbody sheet metal, and the thick metal plates that reinforce that mounting point. Another Volt owner in my area "just tightened" it which allowed the hitch to move ever so slightly at that D/S mounting point. Extending that movement out a foot or two where the bike rack is, it'll look like the bikes are going to heave off the rack. Bottom line, get a big-ass breaker bar and tighten the heck outta the D/S bolts; it'll probably even flatten some of the sheet metal. That's OK - you want a super solid connection. But don't over tighten the passenger side bolts.
By using a hitch rack, you don't suffer the miles per charge reduction from a roof rack. Plus I can carry two bikes without disassembling. Do I trust the hitch? Definitely: I'm carrying a Yeti SB6c worth 3/4 of the current value of my Volt! I'm not using a stabilizing strap either - it's solid, no bouncing.
By using a hitch rack, you don't suffer the miles per charge reduction from a roof rack. Plus I can carry two bikes without disassembling. Do I trust the hitch? Definitely: I'm carrying a Yeti SB6c worth 3/4 of the current value of my Volt! I'm not using a stabilizing strap either - it's solid, no bouncing.