I had installed one those Red Key Switches last year on top of my battery box lid. Although we never had any problems of it falling out or losing it, we did have sporadic problems with it making a connection. Worked when it wanted to. All connections were tight, just had a mind of it's own.
Finally had enough and purchased and installed this SEAFLO battery Kill Switch. Perfect! Works first time, every time. No more second guessing if its going to work or not.
https://www.ebay.com/itm/SEAFLO-ON-O...53.m2749.l2649