Please note, all acrylic / perspex poles tend to deflect over time, especially with fluctuations in the weather / temperatures. For this reason we recommend you have a small drape of the curtain on the floor, always have a centre bracket & in cases of wider poles have passing brackets & passing rings to give added support at the quarter way point. From time to time you may need to turn the pole in the bracket & re-secure depending on the deflection. Over time the pole will straighten before needing to be turned again.
Add a minimum of 15cm either side, preferably more, but for full curtains or wide windows allow at least 25cm if you have the room, excluding finials (decorative pole ends).