I have done no end of tests and there is nothing to beat simple heavy mono fished slack line style. None of the tubings or "heavy" leaders follow any but the smoothest of lake beds because they simply aren't heavy enough and are too stiff.
My question would have to be "why go to the trouble to find the best, least visible main line that you can buy and then thread it through a length of "hose-pipe" where it will be closest to where you want the fish to be. Exactly the same can be asked of any of the leaders. They are 3 or 4 times the diametre of your main line so will be much easier for the carp to spot.
My honest advice is to stick to simple running rigs with light leads and no tubing no leaders and no back leads of any kind. Just fish with the line slack and let everyone else pay silly prices for items of tackle that they don't need. Since I switched to the simple rigs my catch rate has quadrupled.
Hope that helps mate.
Keith
Thanks for the post Keith...I have been thinking of going tubing free. The only reason I have ALWAYS used tubing was for anti tangle (As i was told from the start), and protection for fish from the mainline, have you ever experienced lifting scales without tubing?
I have been wrapping my brains to try and get a 'free'er running rig', and this was something I thought of.
Cheers
Matt