This is getting repetitive: installed more nutplates of varying sizes in varying locations, over a period of several days.
Unfortunately my attempt to drill holes for the Apex tiedown bars did not go well. The first one suffered from layout issues that made the holes off-center. Bottom line is that a ruler plus marking pen is simply inadequate for accuracy. Looking online, it appears that others pioneered this mistake well in advance of today.
On the second bar, I was able to produce a unique piece of art. The work scooted under the edge if the stop on the saw. Result: wrecked aluminum and broken tooth on the aluminum saw. Luckily the blade held together, so no amputations. Ordered a new blade, two new hunks of aluminum, and a beer.
BTW, for others building RVs, these apex plates can be ordered with the pain of tapping the hole already finished. See Cleaveland Tool's website.
Total Time: 3 hours