Spent most of the morning squaring up the fuselage in order to drill out the upper tail area. With all three dimensions at play, I found it challenging to get all the right parts stabilized and clamped dow at the same time. Of the 1.5 hours I was in the (freezing cold!) garage today, only about 30 minutes was spent drilling rivet holes! Nonetheless, it's drilled out and in good shape now.
UPDATE: Turns out I had a stray piece of wood (1 x 2) under the fuselage when I "squared up" the horizontal tail (HT) area. After discovering and removing the piece of wood, the HT area was definitely not square. The good news is the parts I incorrectly driled out are relatively cheap and available so their replacements should be arriving in a few days.
The Johnson Laser Level - a key tool for ensuring a straight and square fuselage.