Ah, yes, again we re-visit the MS vs. CM conversation.
A few facts:
The heavy wall MS has about the same yield strength (resistance to breakage) as the thin wall CM.

The weight saving is entirely due to: less metal used.

For a tube of given length, stiffness (resistance to bending or shape deformation) is almost entirely a function of its outside diameter. The relationship: R ~ OD^4.
Increasing a tube's OD by 25% (e.g., using 1-1/4" OD instead of 1") increases its stiffness to 244% - it's more than doubled.

Curved tube: avoid whenever possible, when stressed it will bend where it's already bent. Shorten the tube by running a strut as close to the center as possible.

The next factor is the wall thickness - pretty much linear (add 10%, get 10%).

Last is material, but CM and MS are almost identical, in fact almost every steel alloy (and all steels are alloys) has the same Young's Modulus of elasticity. Any steel is much, much stiffer than any aluminum alloy in terms of section thickness (not per pound), and stiffer than titanium.

The other big secret (meaning, no attention paid to it, although it's very important)? Minimal length of any unsupported (uninterrupted) span.
A tube 4 feet long is almost twice as stiff (+95%) as a tube 5 feet long. This is why triangles are used.
Unless the open area is necessary for something (driver exit, engine bay) all rectangular shapes should be shortened with a diagonal, even if it doesn't extend the entire height of width. Since these are generally not part of the required certification structure they don't have to be minimum diameter - they can be 7/8" OD and still help (saves weight and money).