cucumbers inside cages

I am growing cucumbers inside cages made from rewire (some left-over tomato cages) to conserve garden space. My concern is whether the vines are sufficiently supported by the cucumber plants' tendrils only during production or if the vines need additional support. The cages are 5 feet tall and 2.5 feet wide. I'm hoping each runner will grow over the cage and grow back towards the ground helping secure the vines. I have been feeding the individual runners up inside the cage and the tendrils then twist on the wire supporting the vines. Advice will be greatly appreciated so if necessary, I'll have time to tie the vines as the plants are still in the blossoming stage.