So, in any point I said that it took 0 slots… As I put it only as armour, it takes 8 slots. So, there are only 4 slots remaining before there are some penalties. And that is on purpose: the Spider-Human cannot use items created for human. The idea is that in reality they will not be using items at all. That is the “unbalance” of using the background that has armour 4. Besides, remember: you can, for sure, adjust that on your table :)