That is exactly what I am looking for. I have a stock of target arrow shafts that I use for jigs, spars and fuselage stiffeners in profiles. Since I use Morris controls I have never needed one for a pushrod. Not sure but I think they are actually lighter. Where do you get your LH bolts and tap? The arrow shaft is thick enough that you could make a tiny strap wench to do the adjustments and that solves all of my problems!
I suppose I could still use the DuBro turnbuckle and make the shaft with 2 RH receptors. FYI - he last post on the Tom Morris forum was in 2016.
Sorry -- I was going lightly on the definition of "turnbuckle". I just use RH thread on each end of the shaft, and remove the ball end from the horn to make adjustments. I feel this is better, because in the unlikely event of
a water landing the pushrod turning, it'll back out of one end just as much as it screws into the other. I was going to send you to McMaster-Carr for stuff, but they don't have much LH stuff that small -- although they do have one LH 4-40 screw, if you dig for it. It looks like
MSC has left-hand dies but no screws, they should have suitable-sized drill rod and left-hand taps to match.