That used to be a issue say 8 to 10 years ago. Now that should no longer be a problem. The first thing I would say is to check the length of the housing at the der. All housing should follow the natural curve of the housing. If it is too long at the der then you will get sporatic shifting. A good site to look at this stiff for yourself is here:
http://www.parktool.com/repair_help/index.shtml