I bought some straps (the 'lightweight' 200lb version), and just strapped the middle of the bike to the carrier as well. Everything actually held together really well until I went off road... After ~10 minutes of rocking left and right, the carrier had come loose (screw came slightly undone) and started rocking on the bars. I was able to get it tightened, and was off again. I'm going to use some loc-tight on the screw that clamps the carrier to the bars, that should prevent any further issues.
Overall, quite happy. Though the rear strap down has some rust on it, that's said. The rest of the mount is fine though.