andanista - I echo erice's comment about the 5.2 method, under the tramp. N5.7 & N5.8 were 8ft beams. Those boats could have jib sheeted to inside of the hulls, and angle was OK, a compromise to a simple solution i.e less cluttered tramp than N5.2. But, for the wider beams of the N5.5 sloop, basically an updated 5.2, they developed the 4-way wire rig. If you don't have or want this 4-way, but don't like the "too open slot" of your jib, you need to move the sheeting angle inward. Either make jib block attachments points directly onto the trampoline (some Tornados used to do this before new rig), or do the under-tramp wire method like on old N5.2. I used this under-tramp wire when I converted my N5.5 uni into a sloop. However, instead of wire, I used spectra line (no stretch but doesn't cut like wire), and instead of mouting exactly aligned with hulls, I angled the two "wires" slightly in at the front. When you have a "4-way" system, you pretty much only use two "corners" of the 4 possible settings [inboard+forward and outboard-toward stern]. I get both settings with only one adjuster line along the "wires" - like the old N5.2 system.

jim casto
nacra5.7
nacra5.5uni/sloop

Jim, thanks for pm about daggerboards. I solved that already. About the under tramp system, please explain in more detail. You have two wires, one each side, almost parallel to the hulls or almost perpendicular (or in between)? Did you attach the line to the tramp?
I got a better line and stretching is not a problem now. I am pretty convinced that the ideal point for the block is forward of the tracks. Next time I'll run the line from side to side but attached forward of the track, at the forward attachment of the bungie for the daggerboard. Hopefully it'll be close enough. Then I'll probably run it under the tramp and if necessary angle it a bit forward. For high wind I may have a second setting, attaching to the the track forward position and runing the line with more angle forward. Regarding adjustment, I'll keep using prussik knots, it's very simple. You can adjust during a tack very quickly, which is good enough for me (not racing).

Prussik knot: