The stiffener is also longer so it provides reinforcement to the rail where the rear arm mounts.
The stiffener can also serve as a repair kit for rails that are already cracked at the rear arm mount hole.
The rail saver kit also includes a cross shaft to provide additional strength. The mono shock II suspensions have a similar cross shaft behind the rear pivot arm. The shaft gets mounted using the factory rear idler wheel mount holes. The rear idlers then get relocated behind the BOP stiffener.
Sell price for this kit will be $155. It will include a LH stiffener, RH stiffener, cross shaft, and all necessary hardware as needed. Just one factory Yamaha outer stiffener lists for $131!!