I was thinking your foot against a wet sycamore tends to slide. The anchor point wouldn't move, but I don't know how your foot wouldn't slide on some of those no matter how much weight is places on the aider foot loop.
It doesn’t move because it can’t move. The leverage created, doesn’t rely of smoothness or roughness of bark. It relies on you following procedure. Put your foot where you’re supposed to, weight your feet appropriately, use lb effectively, it can’t move. Stretch too far, have your aider not in full contact with the tree, let your Lb slide below your knees, and you risk slipping.
It could play a role for the small concentrated surface area of a boot tip. But you’re wrapping the aider about 40% of the tree’s circumference. And the weight is distributed very evenly across the inside surface of your entire boot, and the entire length of the aider. You’re beyond the critical low point of friction needed, and the forces are distributed in such a way, that smooth or wet bark don’t matter.
I am confident you could figure out a way it matters if you really want to try. I’m just telling you I’m going on three seasons and probably 100+ climbs on all kinds of trees in huntjng scenarios, and another 100+ In yard and showing friends.
Everyone has a pre conceived notion of aiders due to seeing 280lb fellers flipping upside down on YouTube, or scraping their own shin not having a good grasp of what they’re doing. I’m not telling anyone this is a good or bad idea for them. What I’m telling you is that there is a completely different concept and execution that is fully outside of what you’re used to. You can turn it into a sh*tshow on purpose in a hurry. But you can follow a few simple procedures, and have a really effective way to get up a tree.
I definitely think all climbing methods are closer together than farther apart in “effort, skill, money, time, fiddle factor, annoyance” when taken in totality. But if I were picking one for being slightly outside the margin, it’s bolts and an aider.
If you were extremely risk averse, you could add your tether on the climb(in addition to LB), and eliminate almost all fall or slip risk. I don’t, because I’m religious on 3pt climbing and use my Lb effectively. I use my tether to cross limbs, and on wet leaners. And if I recall correctly, on one of those sycamores, to cross limbs.