Floyd Sense wrote:

Anyone know if the Shimano DX rear derailleur will shift properly on a 9
speed when using the Ultegra STI brake/shift levers? I'm currently using
that rear derailleur with an 8 speed setup with Shimano barcons in indexed
mode and that setup shifts perfectly.

Yes. 7 speed mechs are compatible with 8 or 9 speed shifters, whatever
Mr Shimano says.