I have to agree with black ice. It is a cost vs risk ratio. The original arms were made in a new casting process (vs forged) that was proposed to be as strong as forged but cheaper and lighter, However there were found to be imperfections in the arms; one cracked and therefore replaced. Arm failure at high speed could be lethal. I quess lost power to the wheels due to a-bolt failure is not thought as being as dangerous (less likely to initiate some costly and high profile law suits).. I e-mailed ricardo about the problem but they are deferring to Ford.