Another yellow late summer bloomer that I wouldn't be without is Sneezeweed (Helenium 'Double Trouble'). Ours grows in part shade under our small-leaved tree canopy and has done just fine for ten years or better. It gets to around 5' tall and bushes out quite a bit, but requires very little root space. Depending on how deep your shade is you may want to stake it, but it really hasn't been necessary here. Some years I do, and some I don't. On years I don't, it just hangs over to the sides a bit more. I'd think that might be just fine in your situation.
Plus, it needs no extra water or care once it's established. It just gets taller if you water it. The blooms don't seem to be affected either way.
