I removed my boom today [04/27/08]. Five & 3/8″ [or 136.525 millimeters] of boom was inside the frame. The boom wall thickness [measured with a micrometer at the frame-end boom opening] is 1.20 mm at its thinnest and 2.10 mm at its thickest. The crack is on the bottom [painted red] of the boom, which is thinner than the top of the boom. Although I cannot determine where the crack began, for the most part, it runs along the bottom-center of the boom. On the frame-end [bottom of this photo] the crack makes a near 90-degree turn to the left and on the crank-end [top of this photo] an opposite 90-degree turn to the right.