Charles...
Glad to see you moving at this rate on your 'Z'. Flying wires are sharp, do you have different threads on each end? (right hand at one, left hand on other) Can't imagine how you'd get tautness by any other method
My Gee Bee R1 had flying wires, but was half the scale of your 'Z'. Method was eyelets in wing, pants, fuse...a single solid stainless wire was strung thru, twisted loop ends soldered after passing thru 1/32" holes bored in a square nut, which were drawn into tension with a 2" long machine screw, counter bored in the center of the fuse bottom. (screw turned thru bored center of 3/8" dowel gusseted in lower belly)
R1 was full fused, bulkheads & stringers, scale placed planking, silk covered. Unique in 1974, only C/L Gee Bee to be seen. Whole rash of 'em seemed to follow, mainly R/C...but when we flew in Santa Cruz, it was the only dog in the yard.