That's true Kane - but I got no ''retract'' in this system, the tube which is out of alignment (the one from the 5 way valve to the QEV) is the main supply to the buffer tank. Retract will be by spring dampers or bungee chord.
Its still a good option to use smaller tubing though, lets see how the actuator goes and then proceed from there - I only need to lift 17kg, and if my calculations are right, using a 63mm dia actuator at 10bar should get a force of 300kg, should be enough I hope might also consider lowering the pressure to conserve Co2 and get less stress on the whole bot...