Tool Holders

[Rickabilly]

Keeping in mind Darren that you still need to get centre height right, and in a small bore a change in centre height will change a number of things including for example the effect of a move in the x axis of 0.010" won't take out 0.20" if the tip is substantially below or above centre height, this is a small issue, but in addition to the rake and clearance angles being confused, why take the chance, I would investigate just how hard the holders are and either drill and fit a widget as you have described, or do as I do and set up the boring bar using a square, with the stock sitting on the side of the holder and the blade holding the top of the bar in the correct orientation, Easy peasy. No cost or effort required, I would like to take credit for this method but I can't, it was a standard method used in a CNC lathe I was trained on back in the eighties.
Regards
Rick