Not a suggestion, it's the rule. Now rules are open to interpretation of course, but its pretty clear what its asking for. I wonder what happened to re-write the rule

From 2013 Rule Book:

""D" Bar installation for full bodied cars: For front-wheel-drive cars, with complete OEM floor (from firewall to rear of the trunk) and rocker and sill boxes, the 1 1/4-inch x .058-inch CM (.118-inch MS) "D" bars (when required; i.e., when the main hoop is not welded to the frame) may be welded to a 1 5/8-inch x .083-inch CM (.118-inch MS) crossmember welded to the rocker/sill box via conventional 6-inch x 6-inch x 1/8-inch-thick plates."