Those are in the place of the sliders on the T-Rex cages? Brilliant!
I think the only mod I would make is to partially cut through the bolt connecting the pegs to the cage so that in case of a tip over the bolt would shear before bending the cages. I'm think I'm going to try and find similar pegs.It's a threaded lug welded to the cage. Made me a adapter to mount the pegs.