Snake,
I don't have an [words=https://shop.mattersofsize.com/products/sizegenetics-penis-extender]extender[/words] device. (Yet!

) But what I have read regarding the tunica says that its normal tensile strength (at around body temperature) is roughly 4.5 pounds. That means you would need to exert a force just slightly greater than that to actually make those collagen fibers lose connection to their adjacent fibers. Note: I am talking about the force necessary to cause a "failure" of connection of these tiny triple helixes.
You can technically "stretch" the tissues of the penis at any level beyond their normal state. "Stretching" the fibers is good for Penis Enlargement too. "Failure" or "tearing" is not necessary to gain size, it simply speeds up the mitosis process. However, "just" stretching the fibers does help to realign the fibers in the direction parallel to the [words=https://shop.mattersofsize.com/products/sizegenetics-penis-extender]traction[/words] force used. This alignment itself adds to size on the macro scale, even if they return to their natural length after the [words=https://shop.mattersofsize.com/products/sizegenetics-penis-extender]traction[/words] force is removed.
However, the most important thing to keep in mind, from the studies I have seen, is that all things being equal, that increasing the time under [words=https://shop.mattersofsize.com/products/sizegenetics-penis-extender]traction[/words] is more efficient to gains than increasing [words=https://shop.mattersofsize.com/products/sizegenetics-penis-extender]traction[/words] force. The cell cycle that we are trying to induce or accelerate is a form of mitosis. The most important point of the cycle is when we cause a greater separation between cells, encouraging "parent" cells to split and create "daughter" cells. The rest of the cycle is the time taken for the daughter cells to gather nutrients/chemicals in order to grow to the original size of the parent cell.
From some literature, the time taken to cause the parent cell to split into two structurally identical, albeit smaller, daughter cells is from one to two hours. The rest of the cycle, roughly a twenty-four hour period, is spent by the daughter cells in gathering nutrients and growing to their parent cell's size. (Now it should be pointed out, that if there are not sufficient nutrients present in the system to accomplish this, the "recovery" cycle will last until they are accumulated)
So what is the advantage of stretching outside of the golden "two hour" phase? Well, first, at any point in time there are daughter cells which have not grown to parent size yet. So there are always new parents to be encouraged by [words=https://shop.mattersofsize.com/products/sizegenetics-penis-extender]traction[/words] to split at any given point in time. Secondly, if the parent cell getting ready to split is in an elongated state when it is ready to split, it passes on the information, (DNA, rather, RNA I think in this case) of it's structure to the daughter cell it produces. The daughters are instructed to replicate the parent. If the parent in elongated when it splits, the daughters attempt to replicate that elongated state as well.
This is probably the best explanation as to why time under [words=https://shop.mattersofsize.com/products/sizegenetics-penis-extender]traction[/words] force is significantly more important that the [words=https://shop.mattersofsize.com/products/sizegenetics-penis-extender]traction[/words] force itself. The only benefits of high [words=https://shop.mattersofsize.com/products/sizegenetics-penis-extender]traction[/words] forces come from when you exceed the tensile strength of the triple helixes themselves or to encourage as many different cells as possible at once. However, if this level of force, severely retards time in [words=https://shop.mattersofsize.com/products/sizegenetics-penis-extender]traction[/words], (less than one hour, or preferably, a little over two hours continuous), it most likely decreases efficiency rather than increasing it.
In my humble opinion, from everything that I have read, IDEALLY, [words=https://shop.mattersofsize.com/products/sizegenetics-penis-extender]traction[/words] would be best if any significant force of [words=https://shop.mattersofsize.com/products/sizegenetics-penis-extender]traction[/words] could be maintained continuously. What feels "intense" on the macro level, has little to do with what is happening at the microscopic level. Ask yourself this, who would gain more from Penis Enlargement? A man who did the most intense Penis Enlargement workout imaginable for a month, or a man who did a moderate workout for over 30 years? Now shrink that idea down to hours?
Tom