Thank you! You're correct, the extra tenon stays. I just haven't routed it flush with the bottom of the pickup cavity yet. The idea is to have a neck system that works as either a set-neck or bolt-on, the only change necessary is the addition of bolts. In either case, the extended tenon helps: as a set-neck, it's a good bit of extra gluing surface; as a bolt-on, it prevents the alignment from ever shifting out of place a la Fender or Ibanez (I've had to realign tons of these for myself and others). Also, I'm not sure if you can see or not, but the tenon extension's thickness will be about 0.25" (6.35mm), so it does have a fair amount of strength on its own.