I learned a great trick for stretching a tension spring, to get it back on the hooks without too much difficulty.
Stick one end of the spring in a vice, push it right over to one side, and poke a washer in one of the gaps between the coils.
Push in the opposite direction and stick a washer in the opposite gap
Continue to do this, adding washers until the spring is long enough to enable you to hook both ends on the hooks.
When you extend the spring by putting the centre-stand all the way down, all the washers fall out.