When you order chassis, you get a longer SS screw and longer nylon standoff as well. The chassis has the room to take you higher...I suggest a nut under each of the plastic control board standoffs. Keeps those long screws secure. You also gain 1 nut width of extra spacing away from the backplanes. Should be enough thread left to use a nylon washer and nut after the control board is mounted.
Those long plastic standoffs tend to "relax".
