Your build looks very nice, I'm sure it will sound just as good.
If you want to "dress" up the OPT wiring, you can bundle them along the side wall, then "cable" tie them with a back [loop] stitch using sewing thread, tie off at the ends. Then add two sticky back nylon loops on the side wall for each bundle, one at each end as appropriate, then use nylon tie wrap to fix the bundle to the SBNL - neat. Do all your testing first.
Shannon's board sure makes mounting all the hardware easy.