When strip building canoes and kayaks took off as far as popularity, the trend in books and instructions was to do your final sanding quite smooth like 150 grit paper or finer and I think this might have caused some adhesion problems or at leas a compromised adhesion. I do my final sanding with 100 grit with the grain. My wood gets a tiny bit darker but the epoxy just has a bit more to grab on to. I'm sure I use a little more epoxy doing that, but I am building a boat and never had any de-lam problems. I had that West booklet years back and I think they recommended around 100 grit or courser for the best adhesion on wood joints. So it made sense to me to not go too fine on the surface sanding.