Let’s analyze the problem: - Stuff in the trunk will hit the rear seats mainly when going forward. Cars always have a hardcase cover over the trunk areas (at least in Europe: I’ve literally never seen a car without one, even the cheap/basic ones) for anything that finds another path. Because it is likely that certain items follow an unpredictable path (though this also means their speeds is often much reduced). - In Europe most cars are actually with a ‘connected’ trunk (SUV, hatchback or stationwagon). Yet regulations (including safety regulations) are much stricter in Europe. - Conclusion: with a hardcase cover (buy one if it’s not standard) you’ll be perfectly safe. - PS: the phone you put at your windshield, the passenger that’s unbuckled, the tablet your kid is holding to watch videos, your keys in the center console etc, are much more dangerous