keeping sub box in its place....?

[bigtigexplorer]

That sounds like you've got it covered then. The only thing I would recommend would be to use a lock that is protected against bolt cutters.

Here is a link to some Shrouded Padlocks that protect against bolt cutters. I'm using the "Titanium Reinforced" series.

 

[Defiantguy]

I use ratchet straps, since I move my sub box around quite a bit(for cargo space).