Although the front spar had been damaged in transit, the rear spar was OK.
I had still not figured out how to improve the quality of my countersinking of the tailplane spar flanges, so research was required. The problem is twofold. The spar web and/or the flange flexes when being drilled, and the spar flange is not exactly at right angles to the web.
Eventually I came up with a jig that would probably do the "business" for both the front and rear spar. I had plenty of "scrap" spar to work on, so I practiced until I got good, but still not perfect, results. Once again my mobile phone was put to use as an "inclinometer" (free application for iPhones). The application seems to be accurate to one degree, but my jig is only good for 2-3 degrees. This is still enough of a variation to be visible, but I hope "good enough". Pictures show the replacement rear spar after drilling.
