Just a thought...
In tree climbing, if one is footlocking with a hand ascender, a backup prusik is required. However, if the prusik is located below the ascender and there is a failure to engage the line, the ascender will slide down the rope and take the prusik with them. (The same way you slide the prusik by hand.) For this reason, the prusik must be placed above the ascender. I'll post a photo illustrating the system. I'm bringing this up because so many use a ropeman on their tether. A prusik below it won't stop a fall. A stopper knot on the end of the tether would, however.
Okay, for some reason, I can't find the illustration I was looking for. I am posting a photo of a long prusik loop similar to what I used with ascenders. If anyone needs more of an explanation, let me know. I'll find an illustration, or just make one myself.