This is progressing very slowly - two steps forward, one back!
I think my basic plan was good, but the task order needed refining. In the end the progress has gone in this order:
1) Drill the four inner interplane struts and thread with mono for the landing wires. The mounting bracket at the outer end of the rear landing wires was also attached to the mono prior to mounting the struts. ( These wires will not be secured until after the upper wing is in place).
2) Attach all the struts. (Jig not needed as the one good thing about the SPAD is that all the struts are vertical and parallel)
3) Attach the inner flying wires (by inner wires, I mean the rear one of the front pair, and the front one of the rear pair) to the fuselage/wing attach points and super glue them to the rear face of the front centre strut and front face of the rear one as appropriate.
4) Fit the cross-braces on the inner struts, trapping the landing wires between the strut and the cross-brace.

The next step will be to repaint the cross-braces and a bit of touch up elsewhere as needed, rig the inner interplane struts with stainless wire, then attach the upper wing. When all that is dry, the rigging will be completed and tightened if necessary with heat.
Thanks for looking in!
Ian