The only issue I see with the formed style is that they are U-channel and not a piece of tube. Still better than a piece of tube hanging below the floor. Once the tube is installed it looks the same from the bottom anyway. I failed to put them in my street Challenger. Big mistake, even a small block 4 speed 12.50 car has tweeked the C-Pillar 1/4 to roof. I like to cut the bottom of the rear frame rail away. Drill a few spot welds and clamp the rail sides to the tube. Push the floor down to the tube at the front a 1/2" or so and it'll all be solid.
Doug