With the diameter of the bolts known, I had to find the right drill bit. So far so good. What did present the first major problem was drilling the holes through the pipe stanchion. I didn't have a secure way to hold the pipe and while the holes were centered and in line on the top, the bottom side ended up cockeyed. My pipe is now air-conditioned. I needed straight holes so I could drill evenly through the mounting board.
Ta-Da. May not be fancy and may have different sizes of bolts, nuts and washers but it is straight.
The weather was actually sunny when I started. The first challenge was getting the old bracket off. Then I put the new one on, only to discover that a) trying to drill through loose metal flashing while hanging upside down, breaks drill bits b) my screws were too short; c) the flashing on the roof prevented the stanchion from standing perfectly straight and d) a sheet metal hex screws holding the flashing on stuck out, tipping the mount even further west. The weather was coming in and I really did not want to go back down the two metal roofs and ladder to get more screws and tools. Fortunately I had my go-to channel locks with me. I was able to remove the broken drill bit and sheet metal screw (the mounting board is now holding the end cap on). I used the long screws from the previous mount but still could not get the stanchion to stand without a list to the west. Everything came off again and I screwed the old mounting board as a spacer. By now the drill battery was dead. I quickly mounted the weather station, oriented it south and made sure it was perfectly level (after all, it's information is going to NOAA so no slack).
I still have one more screw to finish screwing in. The final result may not be pretty but it does go with the patina of the place and NOAA will never actually see it.
Not to forget the fur kids. Koyuk actually had a hind leg over Jake and Jake, right up against Koyuk's belly, had one foot under and head resting on Koyuk's front leg when I went to grab my camera. Both woke up and re-positioned before I could get the picture. But, this is the typical BrownStone pack activity level when I am up in the office.