I would be extremely paranoid just thinking there is a piece of metal constantly moving inside the shock shaft. At any moment may overheat, bind, and create all kinds of bad stuff inside the shock. I know sometimes I am cheap on certain things, and cut corners, in this case have you tried water lines sold at Lowe's. Its about 13 cents per foot, very strong clear plastic. Another option would be pistons from smaller scale rc, 1/8th, 1/10th, and drill the center hole to fit the shaft diameter of the larger shocks, or o-rings from those Harbor Freight tray sets. Those fancy vacuum lines, yellow, red sold on Auto Zone for those ricer intakes teenagers put in their cars, are very strong. I use those as spacers for the King Motor X2 a-arms and pins, and hold very well, if it works fine on such area, would say it is good for the shocks.