Instead of putting just tons of coke in the box, if you are able to also collect darksteel ore and synth them into darksteel ingots, I would just do that to conserve space. 9 stacks of coke + 6 stacks of darksteel ore can be compressed into 1 stack of ingots.

If by some chance you end up with more ingots than you can use, you can also HQ them in sets of 5 and sell them on the markets for any of those poor saps that didn't get their BSM/ARM mastercraft books yet. >