In reply to acidduk:
Hi all,
I'm the friend.
I'm going to start this with a warning, part of my job is scientific analysis and validation of ideas and concepts, so this might become very dry.
When reading about attachment of PASs and Cows Tails you firstly get a lot of conflicting results, which largely boil down to 3 schools of thought.
1. Attach your PAS to the tie in loops, else the PAS will wear out your belay loop.
2. Attach your PAS to either the Belay loop or the Tie in loops, it doesn't actually matter as long as you do it right.
3. Read the F*!?~#g manual and do what they say.
As someone who views scientific rational on a daily basis I'm not a huge fan of blindly following school 3. There are definite merits to reading the manual, gear will have been tested in the way the manual states and it's the manufactures who shall be open to litigation should their method prove to be faulty. However it's worth noting that everyone runs to a budget and just because you set something up in one way doesn't mean it's not safe to do it another way, it simply can be down to the manufacturer not testing that way. THAT SAID YOU SHOULD ALWAYS FOLLOW THE MANUFACTURES RECOMMENDATIONS UNLESS YOU ARE REALLY SURE OF THE THEORY BEHIND NOT DOING IT. IF IN ANY DOUBT WHATSOEVER DO AS THEY RECOMMEND.
I hope that last part was sufficiently clear.
Now on the point of PAS's there are two distinct styles, Sling based (Static) and rope based (dynamic). It's worth noting that in the manuals for all rope based PAS systems the instructions state using the belay loop (Beal Dynaclip, Petzl Connect Ajust, Simond La Vache) as your harness attachment point. I've not looked at lots of PAS static systems as my preference is to have some form of dynamic support on my anchor, even if it is just 75 cm of 10 mm rope. Conversely the PAS systems instruction is recommended to be lark hitched to your tie in points.
So fundamentally going from whats written in the instructions you attach static slings to your tie in loops, and dynamic ropes to your belay loops. This brings you to the question 'Are people getting the two different systems confused because they're for the same purpose and erroneously lumped together?'. Personally I think this is the issue.
Now running to the question of 'Is it dangerous to use a PAS in the belay loop?' Fundamentally the Belay loop is the single strongest part of your harness, this isn't an opinion, it's a statement of fact. So there isn't a worry about tying in your loop for raw strength. Drilling down to the root cause of why people mistrust the belay loop comes down to the concept of wear.
https://eu.blackdiamondequipment.com/en_GB/experience-story?cid=qc-lab-pers...
Is a decent enough article but it's also worth noting that the recommendation at the end is not backed with empirical data and is a 'feeling over facts' statement. Black Diamond also published this article showing that a belay harness with 50% cut through still passed the 15kN standard test. One with 75% cut through almost passed, and all with excessive wear way past what I'd be happy passing a personal inspection all still tested beyond 15kN.
https://eu.blackdiamondequipment.com/en_GB/qc-lab-strength-of-worn-belay-lo...
Also, it's worth noting that I can't find any data on PAS wear on belay loops.
Why I use the Belay loop on the La Vache
1. It's in the manual. The illustration is explicit in using the Belay loop, the images on the website only use the Belay loop, the term 'tie-in loop' may be unclear, but Simond is a French company and the French instructions say 'du point d’ancrage' which is a more generic term 'Anchor Point'. It also references the illustration 2, which really looks like the belay loop. Every other dynamic lanyard with a hitch is
2. It gets in the way when hitching from the tie in points. A 10mm rope is not a nylon sling, adding the rope and the plastic safety shell on your tie in point puts it very close to your tie in knot, when cleaning an anchor point it makes tying off difficult because the knot is right next to a taught rope. Last time I was using this I had to drop the tension on the anchor so I could access the rope, so it wasn't doing it's job.
3. I've not seen any actual data on excessive belay wear cause by hitching a rope to it. People can point to the BD article, but it gives an opinion piece at the end, and the only article on Belay wear I can find is also from BD and points that the harness can be essentially wrecked and still be able to pass the safety standard. So when people tell me that it 'might wear the harness' Unless I see something with empirical data showing me that it's dangerous to conduct this I'm going to treat this with scepticism and refer to the BD belay loop test data.
4. I find the 75cm too short when hitched to the tie in, it's basically perfect length at the belay loop.
However that said, if given a PAS comprising a nylon/sling system I'd probably hitch it to the tie in points as it's smaller, and with the loop system it's more adaptable to length. As a preference I prefer some form of dynamic shock absorption just in case something goes wrong.
Feel free to chip in with anything/any data.