i made some butt boards as per mae-ling's diagram and have a ?? on them. as i install them, it seems it would be best to have a row of screws along the outer edges of the butt boards (ie, the high ridges) as well as at their centers (the edge of the 'rock). what i think i am seeing (no screws on the bb ridges yet) is that the bb is not as effective with only screws at the edge of the 'rock; there is not a pronounced bending of the 'rock. it seems the second row at the bb ridges would pull the bb flatter to the 'rock at the bb ridges and thus have more bending of the rock. question: is a second row of screws at the bb ridges necessary/useful, or am i just imagining things? also, just an fyi for anyone who has not used them yet but will. i am having to screw a scrap piece of 'rock to the backside of the bb where it passes over wires. despite the wires being centered in a 2x6 wall, elect wires are not steel rods and some jut out near the bb. as i'm using 1 5/8" screws, the tips could hit a wire if no scrap of 'rock were in there. it is not a big deal, just something to be aware of.