I'm looking forward to trying some limb to limb traversing soon. Besides my main line, I don't have a second line of very large diameter to use for the traverse. My guess is so far that the second line may not have to be as large or have the 6,000ish strength rating of the main line ; I'm thinking this may be because that second line may not be as likely to take a fall, where the first is being relied on through many possible contingencies. In my thinking, it appears the second line is being tensioned, and coming to take the climbers whole weight gradually, and if a failure happened in the set up in that second tree, ( or new limb ) the first line would have been inspected up close, and that set up would be relied on to catch a fall...more like an aggressive swing I suppose. I realize 8 mil would be doable as a main climbing line, but the larger stronger line would provide a much larger margin for error....but as a line to pull oneself from limb to limb, or tree to tree, it looks good so far. Am I missing something ?
In a traverse significant forces on the anchor points and climbing lines can be created depending on rope angles (vectors) and the climber's position/progression during the traverse. It's arguable what the minimum strength of a rope should be for tree climbing and traversing (the minimum strength value would be the same) but I'm not comfortable using a line less than 5700-5900 lbs. strength.
For an open air traverse with all your weight on the traverse line or lines I wouldn't be comfortable using an 8mm line.
You posted this in "Announcements", probably the "Climbing Technique" forum would be better for the subject. Welcome to the forum.