I got the patch glued in last last night so it's been unwrapped this morning and blended in (not fully finished yet). It looks pretty good, I don't know if it will hold up, but it will be interesting.
The pics are a before (rasped out) and after with the patch blended in. They are taken from different sides to try to show the detail better, although it would be easier to compare if I'd taken them from identical positions... can't win 'em all.
I'll probably get it flexing on the tiller this afternoon, it will be interesting to see if it has stiffened that area. ...
I've done that now and it does seem stiffer, showing that the knot was indeed a weak point.
Note the curvy scraper in the bottom pic, very good for scraping those slightly concave areas. That reminds me I could do to sharpen the scrapers, by grinding the edge square and rubbing a new burr on to them. There are plenty of videos about scraper sharpening on Youtube, but don't waste money buying a fancy burnishing tool, the round shaft of a big screwdriver will do the job just fine.