Drill Jig Bearing & Bolt Retainer

The drill jig this is a derivative of is PURE GENIUS and I love it. I've been working on some parametric filament drive plans, that will use a hobbed bolt, so that part is just what I need.

But there's one problem. My scripts let me determine my bolt length rather precisely, and part tolerances... and to make a long story short, if you want to hob at bolt at the very furthest possible point so there's only room for a nut and no bolt extending beyond it, it's not possible in this jig, becaus