So I figured out the “secret” of making the square tubes super strong! I read somewhere the technical term, but I don’t remember at the moment. The secret is attaching a square tube to two tubes in perpendicular directions! This allows for the tube being held in a perpendicular way to hold another tube on its own.
Notice the connected tubes below. The four vertical tubes (the ones that show the hollow end) are attached to the horizontal tube. Those four tubes are then going to attach to the double tubes to give it super strength.
The two drilled holes at the bottom of the picture will hold the horizontal bar in the picture above. The “V” shaped square tubes will also hold the horizontal bar, solidifying the strength of the horizontal and vertical tubes.
More pictures to come, and hopefully the final working product…