@Oertl; You've asked a sharp question. Something that I was considering to add to my previous post, but did not, is that when you route your rope through a tree, you want to try to load each branch in compression, which is the strongest vector that a branch possesses, if I'm understanding things correctly. Put another way, you want to load a branch in such a way that the force is applied so that you are trying to push the branch straight back down its length to the trunk.
What you want to avoid, if possible, is loading a branch in tension, which I think means the way you would try to apply force when wanting to break off a branch from a bigger branch by pulling down on it, away from the bigger part of the branch. Like if you were on the ground, working in your yard, and needed to acquire a stick to reach up for something. You've got a broken branch with a lot of smaller branches coming off of it, and you'd like to tear off one of the smaller ones. So you pull down away from the main branch, and the smaller branch snaps off easily.
I know I'm being way too wordy and unclear, here, but it's tough to describe three dimensional things, sometimes. Hopefully it makes a little bit of sense.
As to your question about "Regardless, are we still talking about a single-point of failure (rope or TIP) with SRT?", I think you are talking about two different things in one question, here. I think using SRT to go through multiple crotches eliminates or reduces the possibility of a suspension point failure causing a fall. I try to imagine what will happen if my highest crotch were to break out using SRT. Where is the next crotch that my rope will fall back to, and the next after that? With DdRT, if the one and only branch your rope is hanging on breaks off, and it is the only rope you are climbing on, you are going to take a fall. With SRT, and multiple suspension points, there's a good chance that no branch will ever break in the first place, because all of them are sharing the load of your bodyweight and gear. If the last crotch in the series, before the line falls freely down to you were to break out, however, there is a good chance that the other crotches that are lined up in sequence will catch your weight and not also fail.
All of the above is a separate issue from a rope failure. If you are only climbing on one rope, and you manage to cut it in half, and you do not have a second tie-in like you are supposed to, you are going to fall. It is the reason it is a requirement that you lanyard in before making any cuts whatsoever, with a chainsaw or even a hand saw. If you cut your climbing line with a saw, and you are also attached to the tree with a lanyard, you now have no way to get down, maybe, but you are also not dead yet. Someone can send you up another rope. It is shockingly easy to cut or "pop" a weighted climbing line with a hand saw.
All of the above is why I prefer to climb using two SRT systems at the same time, on two separate ropes. It helps tremendously with work positioning, and it provides an "alibi" if you run into some kind of an issue with a climbing system.
I've run on too long in this post. I hope some of this is helpful.
Tim
