OK, went ahead with the top rail for the other side... I will cut the tube to install the removable tube... looked like the only way to do it after consulting my structural engineer next door. Although it doesn't look like it from this prospective, the frame rails are narrowing toward the rear. But they need to narrow faster.
I was getting ready to cut a couple of vertical pieces and decided to see if my thought to just put a saw cut through 3 sides of the tube to start "bending" the tube would work. As far as I can tell a saw cut squeezes a little more than a 1/4 inch a foot. The cuts are between the red lines. This seems to be the best way to bend the square tubes, then reweld the cuts.
Yea, now I can take it back to the saw and finish making the 2 uprights.