OK, you win . . . IF you have a push rod tube that is leaking because it's damaged or the seal is bad and you are not in a place where you can pull the engine and FIX it, you can possibly stop the leak or slow it down a little with a spring loaded tube. But it's a very temporary fix. The leak WILL be back. I've seen the cheap nylon tubes warp and twist into all kinds of shapes, and if it's not round, it's hard to seal it with and O-ring.
I don't remember where I saw them, but I have seen some two piece tubes that were adjustable. Instead of being spring loaded, they were threaded and had a jam nut so you could run them out and then lock them in place with the correct pressure on the seals. They had double O ring seals. Those would probably work about as good as stock tubes . . . but for what they cost, you could buy stock tubes, a seal kit and new pistons/cylinders . . . throw in 4 exhaust valves and a little elbow grease and you could have a new top end for about the same price as fixing the leak the "easy" way.
Personally I'd use the duct tape. If it's still gonna leak, no need to spend a lot of time and money on it. :wink: