i used to put shrink tubing on but to me it didnt make any difference plus my m8 used it all the time on a new water we fished together. We used exactly the same rigs and bait except he used shrink tubing, he blanked more often than he caught whilst I caught at least 2 each time we went together. I also think that sometimes air can become trapped in the tubing and make it sort of stand up a bit and look like a spirit level inside which doesnt look too great underwater, I also found this same problem with semi transparent rig tubing such as the khaki from korda, tiny pockets of air in the rig tubing just look so off putting in the water.
I know Fox do different coloured tubing, just buy the one that matches the lake bed as much as possible.
Just a confidence thing with me, I used it, caught less, didnt see any improvements so I took it off, now I catch more and the hook holds are just as good.