Drilling accurate back holes is tough. Getting them directly across from one another is tough. I think if if you etch a line in the Silver Bullet at the the exact spot it might be helpful. You can then use one of those Incra Tiny T's and a steel tipped etcher to draw good permanent lines. If these lines were put in the production of the Silver Bullet it would help. All you have to do then is be sure the block of wood is against the back edge.