Buy yourself a boring head and bar for every hole. Shars Tool Co has a small selection of boring heads for cheap. Now, these are not "tenth's set quality", so you will have to tweak and fiddle to get them cutting to size. But, it beats resetting one boring head over and over again. I am assuming that your spindle taper is in excellent condition and capable of accurate repeat positioning of the toolholder.
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)