Upgrades is kinda overpowered even though it has specific requirements. I should say that upgrades should have stack limits so that they are not that overpowered as well as it's specific slot so people don't use the slot for storing items or putting the same upgrade in a different slot.
Overclockers = max. 10 top slot
Transformer = max. 3 middle slot
Energy storage = max. 5 bottom slot
And since there's a extra slot for upgrades, it should be removed.