The drawer brace is sort of optional, but if you plan to carry heavy gear (100 Lbs or more in one drawer) then we recommend that you use the brace to reduce drawer side-wall deflection. If you want to mount the brace even with the deck when the drawer is fully extended, have at it. This will help the drawer deflection (but not as well as it would work if the brace were in the middle of the drawer) and keep the brace out of your way when loading/unloading gear.