I started tuning a few of the keys, and then decided to find the nodal points before I start taking material out of the underside of the bar. This is so I have an estimate of how far out I should drill and grind.
To do this I rigged this set up so the bar is suspended by 2 rubber bands approximately 1/4 of the way on the bar.
And then you put salt or sugar around the area that the nodes will be. When you start hitting the bar in the center, the vibrations will cause the sugar the align on the nodal points. Then I just marked those areas with a sharpie.
Here is a video of the process....
