The purpose for swept or adjustable spreaders on 80's NACRA's was not pre-bend. The purpose was to stabilize the mast against inversion. The 5.2 extrusion is very flexible by any standards. To stabilize the mast the spreaders were swept aft 1.5 - 2 in and the wires the wires were set "tight". By the early 90's we were using 300-500 lbs on the 5.5 uni, which used the same extrusion.

30 year old memories are fuzzy but some type of swept spreaders was being used on NACRA's prior to 1985. The Hobie 18 had adjustable spreaders in 1977 and I remember a meeting at sailmaker where they talked about the importance of raking the spreaders aft in ~1982.