Today I drilled the attach rails for the rack into the longerons on the floor of the "hell hole," and also began drilling the holes for the various bolts that will hold the rack together. This will probably be the single most complicated modification I've made for this airplane, but it'll be worth it, knowing that all the electrical black boxes will be sturdily-mounted and easily accessible for maintenance. I've decided to move the EFIS backup battery to the top level of the rack, since it's the most likely of the units to ever need replacement. Since it's also the heaviest unit by far, this is another reason I'm glad the rack is built very robustly. [Superseded.]