How do I lock down my spare tire carrier? NOS bottle installs...

[XTwinTurbo]

I'm trying to squeeze my CO2 bottle into the spare tire carrier and it looks like it'll fit and close without problem. Question I have is how do I lock the back (side towards front of car) of the carrier so it doesn't drop down? The problem I'm referring to is the J-slotted hook that allows you to drop your rear carrier another few inches after unbolting the front (towards back of car) side. Anyone have a cheap trick to keep the J-slot from unlatching the carrier over bumps? Even with the carrier bolted down it looks like I can shake it off the back hooks.