I've drilled both the latch and the corresponding 'square piece' that sticks out from the case with a small 1/8" hole and inserted a "R-clip". While normally these latches will not open...taking a spill or extremely rough roads might (and does) unlatch them and the cases can go flying if the mushroom bolt is not properly adjusted.
Also...not pictured...I've drilled a hole through the back of the case (nearest the center of the bike) and continue through the vario mounting bracket. Then, I inserted a 1/4" diameter x 1 1/2" ? length clevis pin (the ones with variable hole lengths) with another R-clip. Put washers on both the outside of the vario mount and the inside of the case. This setup positively keeps the cases from falling off if the 'mushroom' bolt is not, or becomes improperly adjusted.
Most importantly...keep the 'mushroom' bolt properly adjusted. Seems important enough for BMW to have issued the bulletin below.
BTW...this stuff is GREAT for keeping the cases looking NEW! It's CLEAR acrylic that remains CLEAR! Clean first and apply with sponge or soft cloth.
Also..do yourself a favor and before each ride or at a gas stop...try to LIFT upwards on the cases to insure that they're properly secured.
Takes only a moment and can save you $466.95, per MAX BMW!