We are having a lot of success using latex tubing for our non-pneumatic kicker. We should have the ability to adjust the tension and therefor the 'kick' strength. Using a cim motor we can constantly put tension on the tubing then allow it to spring back. We even worked it out so that it resets in just over 2 seconds
http://www.youtube.com/watch?v=30-gyhhBQ7A
we need a better video and I will post one ASAP. The only delay is moving the kicker from the test platform to the drive base