We have a TerraTrike tandem that we bought used, and it has the wonderful Independent Pedaling System. It's great except that the top of the chain rubs the front derailleur cage when we are using the big chainring. Its pretty annoying. Has anyone else run into this, and how did you resolve it? And if you have an IPS-equipped tandem but don't have this issue, what kind of front derailleur do you have?