Look at these videos and see if it helps...
https://www.youtube.com/watch?v=KyusHIVKEJ8
https://www.youtube.com/watch?v=gsnh2z6tXno
I have the V2, not the V3.
In the V2, you do the 'virtual string' thing as shown in the video, then reverse the virtual string.
In your case, each port would have 2 strings of 50 pixels under it. The first forward, and the secong reversed.
In looking at this video, it looks like they have added a zig zag feature.
If I understand correctly, you should just need the one string of 100 pixels. Then turn on Zig Zag and set it to 50
If not, then I'm sure the virtual string thing would work.