My 540 has developed the dreaded 50 mph vibe so i'm replacing the upper arms. I'm also doing the pads & discs at the same time, but is it worth my while doing the lower arms as well?

I hear the upper arms are a very common problem and cause of this vibration, not heard much about the lower arms.

I've also heard that you can fit the arms from a 750 as theyre stronger? Any truth in this, and anything to be aware of if doing this?

Cheers