Cylinders come with no fittings so leaving it out of the retract side to make the cylinder extend quicker isn't anything advanced. To retract the mechanism you may be able to use gravity alone, if that is not enough a light spring like a bit of surgical tubing can help it get started.
For solenoids the only restriction this year is that the maximum port size is 1/8" NPT. A single acting solenoid is all you need for a gravity/spring retract style set up.
It can be very effective both a pneumatic catapult and focusing on getting those 10 truss points. At the Mt Vernon district event team 4918 used a pneumatic powered catapult and and focused on getting the truss points on every cycle along with a triple assist to become the #1 seed.
Check out this thread for a render of their robot.
http://www.chiefdelphi.com/forums/sh...ht=4918+render the only thing that isn't in there is a bit of surgical tubing to make sure that it gets back from the vertical position so that gravity can return it to the loading position.