Ok thank you Matt for the clarification,
I will try going with wood as arms. it's cheap and reliable. I can use the c channels to extend the wood in case I need a larger diameter
But I am not expecting that
And like you said they can double as wind catchers.
If I was deadset on keeping the c channels as arms then I would have gone for Mary's suggestion.
So you mentioned 2 by 4s. I find available for purchase in my neck of the woods
Douglas 50 x 100 mm
or
Spruce 45 x 95 mm
I am not familiar with the characteristics of Douglas. it seems to not be as tolerable to weather conditions as Spruce is. But then again I am guessing that Douglas is also treatable to better withstand weather conditions.
If one can shed a little more light on this it would help a lot. {1}After some more searching I am going for spruce 58x155mm{1}
As for the cross bracing I am holding off on that idea because I am expecting the structure to catch more wind that way. And I have spend a rather large sum on new quality controlled heavy duty components for the guy wires. Things should not just snap like the crap cable tensioner did.
Also I will increase the length of the feet by putting extra 70 x 245mm beams on them. It will help minimize the buckling of the feet and reduce the tipping over ability of the structure
As for the increase in weight I will replace the bottom ball bearing with a taper roller bearing.
I'm thinking inside/under of your guy wires you run cross bracing. Your fulcrum is much shorter this way and should nearly eliminate bowing in the middle.