I used to use much the same method, but a fixture on my drill press table and a stand to hold the other end of the pipe. For orientation of the second cut, I use a 90 degree magnet to hold another piece of tubing in the first notch I cut, then a magnetic base angle finder to set the correct degree of cut on the 2nd notch. Currently working on an indexed fixture to do my notching with an end mill on a vertical lathe, or a very heavy duty drill press...... Trying to make the process faster and more accurate.