I studied how they arrange the oil delivery to the extension cylinders on the full size crane, and I realized they come up with a clever solution.
The oil is run trough the piston rod to the next cylinder. There's apparently two holes running all the way inside the rod from each side of the piston and out of the the top of the rod. If you look closely at this picture you'll see what I mean. There's no rubber hoses, just hard lines.
Unfortunately that's not possible to accomplish in this scale, the rod is only 4 mm thick and over 150 mm long. It would have made everything so much tidier
