Wakeboard tower mounting - Size and material for Heim Joint

[jmcknight]

Looking at purchasing heim joints for tower I am in the beginning process of, but not sure how what size the joints need to be. I think atleast 1/2, but leaning towards 5/8.

Also, i assume everyone uses stainless?

figure i will have the boat for 5 to 10 years, and don't want to have to replace them every year.

Thanks!