I center the amount of weight needed on the bolt (Brodak 1/4 oz weights w/ center hole) and use a small piece of fuel tubing on either side of the weights on the bolt, then bolt the assembly down. The fuel tubing secures the 1/4 oz weights on the bolt so they don't rattle around in the box. Easy to add/subtract weight as needed as the model is flight trimmed.
Brodak shows it this way on their plan drawing for models that use a weight box.
Has worked great for me, and simple to install.