Originally Posted by mycoatl
Ummmm.... why wouldn't this work? I'm a little new to wrenching so please correct me if I'm mistaken.
As far as I know, Indexing is determined by how much cable the Shimano 9 sp bar ends pull, which should match the spacing of a Shimano 9 sp cassette. No problem so far. Assuming the RD has enough capacity for the cassette, why won't it just behave and play nice with the Shimano stuff?
Indexing performance is determined by three things:
1. Cassette spacing.
2. Shifter cable pull.
3. Rear derailleur geometry, i.e, how far the derailleur actually moves from a given amount of cable pull.
For a compatible system, all three must match. The OP has the first two but #3 is different and probably won't work. I recommended he try it but don't hold much hope.
BTW, rerouting the cable attachment to the rd is a badly misinterpreted concept. It was done to make 8-speed Dura Ace rd's work with other Shimano groups. It is not a universal fix for every shifting problem.