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 the length of the finials (decorative pole ends).