Narrow ornamental grass?

[NegroniMacaroni]

I'm looking for an ornamental grass that's quite upright (but not totally rigid) and narrow (+/- 30cm spread the base), height of 60-80cm. It's to go between plants in a tight space. Any ideas?
Would stipa tenuissima fit, or is it a bit wide?

(for a sunny hot position, pretty fertile & quite well drained amended clay soil)

If you'd be prepared to go quite a bit taller, I have a love for arundo donax.

Calamagrostis ‘Karl Foerster’

Have a look at Festuca glauca ('Elijah Blue' or similar), which forms compact blue-grey clumps, or Deschampsia ceapitosa 'Bronzeschleier' (Bronzesheen), which has fine foliage and bronzy flower plumes within your height range and prefers fertile conditions.