Took my time but my install of boom speakers in the lower fairing is done. Here are some pictures of the important steps with comments. I drilled the engine guard and fed the wires inside after removing the guard from the bike. First caution is when removing the guard, don't expect the bolt at the top center to hold the guard from falling off, don't unscrew the bolt, that bolt is there ONLY AS A LOCATION POINT, THERE IS NO NUT ON THE BACK SIDE OR THREADS IN THE FRAME, all that holds the guard is the 2 bolts at the bottom. Next, when you reinstall the guard, relocate the top bolt and if it's a roadglide, like mine, reposition the guard into the fairings lower supports before bolting in the bottom bolts.
Sorry some of these pictures might be upside down, don't know how to fix it.