Well the basics, drilled out the knot....but then took it to work and had a little help from the boys in the machine shop. Was lathe turned out to 26.5mm and milled deeper to 17mm...this should put the loft at 48mm or so. Then used an epoxy to fill the hole up and give it a bit of weight. Knot is a super badger from TGN, 24mm x 65mm. Now to head to the store and get some marine epoxy.