I use Associated B44 posts, drill holes at 75mm apart. Then I Countersunk 3mm holes from the bottom like in this pic, and insert a M3x6mm csk screw with a lock nut. This acts as a stopper to prevent movement of the battery horizontally. To clamp it down, I use schumacer Mi3 touring car rear shock towers as a battery strap, because it has a perfect 75mm spacing , and it was on sale at my LHS for almost half the price of the associated bars.
