Extending net curtain rail, including hooks - 180 to 320cms (Bernards Heath AL1)

It nominally can extend to 320cms, but when I used it in a 240cm window it kept twisting and dropping off the hooks. It could be because the hooks were only screwed into plaster and could twist, or it could be my nets are too heavy. It will probably still be OK for 200 or so, especially if the hooks are screwed into wood or somehow prevented from twisting round, or longer if supported in the middle. All my other window nets use them, but in smaller windows. The skinny end has some small kinks in it (see photo), which you could perhaps bend out or reinforce to restore full strength.