Using stainless or aluminium solid in a 4 link.

i currently have a triangulated 4 link which runs all stainless bars and rod ends.
im looking at making new lower arms that are longer and was wondering if i could use 1 inch stainless square solid or would i be better off staying with 1inch solid stainless  like i currently have. another option is 1 &1/2 inch or 2 inch solid aluminium round rod. i  have access to both types of material and  i just want something i dont need to stress about with regard to fatigue and failure.

 
there is no welding on the bars at all. both ends are adjustable with jam nuts so its only a matter of machining threads into them.

 
thanks heaps

zac

The problem with either one of those materials is that they come in so many different grades that have completely different mechanical properties. Also both aluminum and many grades of stainless are not good with stress reversals which a 4-link sees quite a bit of.   If you were NOT going to mount the bags on the bars, you could get away with either. I would still keep a constant eye out for hairline fractures that could quickly turn into broken bars.

yeah definately not mounting the bags on bars.  the alum is t6 6061 grade. the stainless is 316. thanks for your prompt reply dude.