2 removable crossbar tubes of the rollcage bolted to the cage proper. Welded tabs under the deck pieces, rollcage and support crossbars all align so locking hitch pins and/or locks secure the deck to the cage. The support crossbars aslo have plates to support the deck pieces.
Anything really heavy under the deck like that supply box is bolted to plates under the bed. The toolbag and winch bag also have tie downs under the deck so in case of rollover they don't smash thru the deck.
The entire deck locks with the latches you see topside, underneath and in front. I still have to lock the tailgate, then the whole thing will be pretty secure from theft. Then I'm going to go over it again and maybe add some additional pieces to secure the entire deck more than it is now, in a high speed roll.
Overbuild, I say.