SP4/5 had barrel roller bearing fitted to handle the load at high RPM. The concept was dropped due to service life and cost it appears. Ducati seems to increase preload on standard fit bearings to deal with the extra power as models advanced. Case material probably changed along the way as well.
Steve R and myself fitted them to our 888's. I got about 16-18000 km and Steve some where similar before they flogged out. I believe they were lifed at about 25000 km.
