Hi Don,
Fishing stores have lots of good things for scale(pun) modelers!! Swages, ss cable, wire, etc. The fishing line I use for rigging is spectra line, also known as Spider Wire, Fire Line, etc. As strong as kevlar, and way easier to work with. Thin ca holds the knots. I've not used steel cable in a long time, but I may again since converting my stuff over to 2.4.

Your wood angles sound good, and the ply gussets will help a lot.

John