Excellent tut, Dutch!
Quadlining is a great way to start training off. It accomplishes a few things for me, which I appreciate very much over other forms involving topping/fimming:
a) that "X" shape. Perfect way to get started off when you have a square space to fill up.
b) quicker filling in of the canopy, thus less veg time.
c) better than a mainline or manifold in terms of time it takes to get it done. With a manifold/mainline approach, you need to cut twice, where with a quadline you just need it once to get the same resulting number of tops.
They really are similar ways to do the same thing, but the quadline also keeps node 4, where a mainline/manifold just keeps node 3.
Now if I were going with a wide and narrow space, a mainline may be a better approach, or even a flux for that matter. But you're also extending your veg time too.
Since I like to keep things as simple as possible, grow setups notwithstanding
laugh
, I always allow for a square growing space for the plants. So the "X" of a quadline works just right!