I have tried to craft this several times. I am 59 Woodworking and have failed about 25% of the time. That, coupled with the fact that I have recieved bonecraft skillups while crafting this, leads me to believe that this synth uses Bonecraft as the secondary skill.
Edit: Oh, my Bonecraft skill is 0, so it is possible to make this with just woodworking, but don't expect an HQ. That's what I was going for and didn't get it.