All shrould line are equal length regardless of the number. I use 3, 4 and 6 lines. 4 and 6 mostly on competition mylar chutes, but all 6,8 or 12 ends are attached to the canopy parallel to each other. When they are pulled in at the load end of the shroud loops, they "even out"
As Greg menitoned the illistration is not to scale. but even if it were the lines Wouldn't look like they were the same length.
Steven: I'd be very careful what type Fishing line I'd try to use for shrould lines.
most monofilament lines will be very stiff and unruley to handle. Braided nylon line would probably be OK, but i'd say away for Spider wire or other Spectra blends as it can't take even a little heat. We use it sometimes for Burn strings with HD models
That's one of the reasons I mentoned the Kevlar thread. it looks like it's to fine but it's much stronger then it looks and it's Heat resistant. KEVLAR is not flameproof.
You might also want to try buying Kevlar line on-line from the Thread Exchange. they have a ton of different lines to choose from if you thing the 13lb test material is to light.
By the way Kevlar lines also make Excellent Shockcords and/or Anchors.