Very impressive Rob!
I am watching your updates with interest as I am pretty much doing the same thing with my WH20 and you are a few steps ahead of me. I too had to replace the headbox back section, and at the moment I am trying to decide if I should buy a drill press to put the vent holes back in or do it free hand
When you replaced the braid, what size staple did you use? I have been looking to get the same size as the originals, which I can find (71 series staples), it's just the actual staple gun that is hard to find at a decent price. Best local one I have found is around $169 + delivery, and none of the major hardware chains seem to carry them.
Look forward to seeing some more updates from you