What I need is a 1"x.5" rectangular tube .065" wall and 84" long steel tube that will have the least or very low deflection. I have been trying to educate myself today on the different grades of SS which would be preferable for rust resistance. If I understand things correctly 304 SS is the most common but apparently it is more deflective than carbon steel. I have tried what I believe to be a mild 1x1.5x.065 carbon steel in my application and found it deflects too easily. I am concerned 304 SS will be worse. What I can't change is the requirement for 1"x.5" 84" long. I can use either carbon or stainless (prefer stainless) and increase the wall thickness to .125" but would prefer not to for weight reasons. Specifically, I need the tube to be more rigid and stay very straight and I need suggestions on which grades of carbon and stainless steel will work better. What I am working on is a new invention. I install steel roofs. Roofs with hips and valleys require a miter cut with a circular saw on steel roof panels that are 39" wide. Miter cuts may easily range up to 60". I've invented a Miter Table (pat. pend.) that makes the task much easier. My prototype is entirely aluminum. The miter assembly consists of two rails under the roof panel that support the panel and two rails above the roof panel that support and guide the circular saw. The aluminum I used was stiff enough to not deflect but it creates too much drag on the aluminum base of the saw making it harder to push. That is why I'm switching to steel.