There is a multiplying wt factor of the vehicles wt as it gains speed that the roll-bar/cage must endure in a rollover.I used to have the formula for that,but at the moment I can't find it.That is why winkle free bents,bracing and good tight fish mouth seam welding is critical.The weld should fuse the metal together and not be used as a glue.Out riggers are ok for mounting points as long as they fall within the expected spec a roll-bar/cage would put on them in a rollover.I am not a big fan of floor pan plates for a mounting point because I have seen them deflect or punch threw.I prefer to see direct mounting points to the main frame or out riggers.Triangle bracing to spread the load and X bracing to tie it together are also very important.Again all tight seam welding is a must.