Attach some K2, Everest or Peak 4s to your existing ground box and you will get an obvious leap in performance.
We have always used wooden caps on our binding posts, which is totally neutral and adds no new capacity. In that sense it is perfect. The opposite in fact to using plastics and most metals, indeed we have used this fact to add our all-new features. You simply replace the wood caps on your existing ground box with K2, Everest or Peak 4.
By adding this mix of metals to the binding post you change the performance in the whole box, not only on the used outlet. This means you can fine tune the box so it's optimal for you.