Weight for the setup depends on what type of components you'll use, my current setup weighs 2.5kg, my previous one was weighing more than twice the weight.

Most components are paintball stuff, and relatively inexpensive. The force this system delivers is about 300kg at 10bar, depending on how you connect your ram should be more than enough to throw 12kg robot in the air. Dont have any experience with linear actuators, but I think they make more of a lifter rather than a flipper.

Regarding polycarbonate and pneumatics I'm not sure, but I can tell you that recoil might be a problem depending on how you mount the ram. Mine was mounted vertical, on a base of 5mm hdpe. No problems at all, but being vertical, the force was transferred directly to the floor.

hope this helps a bit...

tmp_20130430_091433-2031416696.jpgtmp_20130503_174106-2093151804.jpg