On a single spar I still prefer two tie in points which should be a minimum when cutting. Osha (at least they used too) says that on single spar both ends of the rope need to terminate to one point on the saddle. This is so that if the spar splits then the split is contained by rope and not rope plus your body. I disagree with there method because attaching this way is (tipsy or wobbly) its not a good way for work positioning. Although I do practice this in a different manner.
I began using my single spar technique after almost being flung out of a willow tree. I was only about 20-25ft up removing a willow on a large wooded lot. My friend was below watching me drop the top out of the tree on this particular day. So I face cut the top and put a back cut in it, I had made a small face cut so that it would snap free a little sooner and jump out a little. Once the top had broken free it had decided to take my saw with it. I am a very stubborn guy so upon refusing to let go my chest was yanked into the tree and the spar was bent over in the direction of the falling top. A couple flicks of the wrist freed my saw and turned this Willow tree into a fine trebuchet. I was sent flying full speed backwards into the woods when my lanyard caught me. Now that I was entirely freed of the the tree with only my lanyard keeping me from going backwards I had no choice but to go down. Alas I do a wonderful chainsaw wielding airwalk (Here is were you imagine me in the air flailing all fours rapidly with one hand still holding an 020t) My left hand grabbed the top of the spar and yanked me in tight and I jammed my spurs back in. As my knees shook and my heart raced my buddy
opcorn: decided that this was maybe the funniest thing he had seen in years. He didnt stop laughing till I was on the ground and let him know it was his turn
This experience led me to conclude that only a lanyard was not safe enough. My lanyard could easily have flung right over the spar and let me go, and with that kind of luck I might as well have been impaled on something when I landed. So I began using what I call the ankle bracelet ( For scared little girls that dont want to fall) hehe. My lanyard is positioned as normal and a topline is tied around the spar so that it drapes down towards my ankles or knees. This way if I get flung it will catch me and swing my dumbfounded but back into the tree also I can make a quick escape if need be (bees,bleeding, whatever) If my lanyard were to get cut then that would be secondary fall protection also. I also use it to rappel between large sections of log that I am dropping and then flick it back down to me. BTW, free climbing to the top in some trees is legitimate in my book and is YOUR PEROGATIVE! but using spikes instead of setting a line in trees that you are not removing is mal-practice.
Pre setting a line is not always a guarantee anyways.
I Pre-set a Acer Negundo two days ago a little lower than where I want the final and when I got to where the final was going to be the winter had caused a long fresh slit in the spar It was still strong but you never know when you are way down on the ground.