Hi!
On my new commuter bike build (based on 2007 Trek 6000 with 3x9-speed deore), I cannot set up the front derailleur in such a way that when I'm in the middle chainring, there won't be any FD rubbing when in the extreme positions in the back. I get, that big+big and possibly small+small will create some rubbing on the FD. But I've never seen rubbing when using middle+[small or large]. 10+ speed systems have trims to get around that. My 8-speed tourer doesn't have that issue. I believe my FD is mounted properly.
Is 9 speed just in the middle of everything and has this issue, or is this not supposed to be the case?
Just for context: chain and cassette are new 9-speed components (KMC, SRAM), and crankset, chainrings and RD are original Shimano parts in good condition.

Thanks!