Finally got our spring today. We cut it to length and thought we'd share our experiences / images so other teams could find comparable items since FRC has a habit of cleaning out worldwide inventories of things.
We found the spring deflects about 7/32" when the gear is placed on the end. Here's some pictures:
http://imgur.com/a/FGELI
It's pretty stiff and holds the gear, even when it's on the very end. Good luck teams!