Fumotos are really meant for stationary motors, it's way too easy to get it open by snagging something with a moving platform.
While I plan for a Stahlbus because of its lower profile, it seems the Fumoto fits well and there is no issue with the swivel plastic tray. So if its closed properly and locked with the tab, then there isn't a way to snag it open. Ofcourse, if something does break the plastic tray, then its possible. However, its also highly likely then it would cause other damage.
I had it on an Accord (which has a lower clearance) and drove it for over 100K miles over city roads/highways and dirt roads. There was never an issue, however, I was also extra careful and drove slowly when going off the roads.