Guitar Neck Can't re-zero accurately !HELP!

I recently purchased an X-carve and have been trying to do a bit of milling. i am still in the wrecking home depot wood at this juncture. All of my drawings are done in solidworks. Anyway the reason for the contact is does anyone mill a tiltback guitar neck with your X-carve? I am having real difficulty getting the necks to finish in with any consistant manor. I am using Meshcam to do the GCode and universal gcode sender. The first issue is that as a single job the stock assumes a rectangle to the largest/highest point of the the model thereby spending a inordinate amount of time routing air. After speaking with Meshcam the suggestion was to create multiple jobs at least 2 one for headstock size and one for heel/radius smaller stock . That seemed logical however the problem I am encountering with that methodology is the 2 jobs lining up on the finished product. That has yet to happen for me. So my assumption is I haven’t passed the dummy stage. I originally tried zeroing off of the lower left corner SW. My stock is layed out the radius is on the Y and the length is on the X . With that zero position the X-carve would never cut my the piece in the center of the stock. So I elected to zero on center and that resolved the cutting in the center. Now to what I am experiencing now. My assumption was that i could do is simply reset stock size to match my Meshcam stock, rezero on the centerline and away I go. However I have yet to be able ( although i am caliper measuring the stock) to get an accurate cut. So that’s my dilemma