I will add my .02 here..
I used the Ruffstuff stiffners.
Reason being, they have a turn up at the body after going up the outside of the rail. For me that was a very nice place to attach my inside cage plates to to make sure that they are actually attached to the rails and there for the cage is also. That mixed with saving the time of any fab work. Time was at a very big premium when I was do these, I had very lil time left to build the Rig for King of The Hammers, stock class.
But after installing them, I still dont think I would waste all the time needed and effort and such to make a set. And as mentioned no one here but RS has the turn out on the top of the stiffner to actually allow you to bolt thru the floor.