I am unable to find further information about the Storage Slips.
Am I right to assume they work a tiny bit similar to a Puppetmaster's Attachments/MMM Vouchers? (Except they can't be removed in that instance).
Basically what I am envisioning here is that we can stash every eligible item item X slip, via the NPC, and then get them out if necessary, etc. I need to reactivate to find out, but wanted to see if anyone has more experience of it.
I'm hoping it won't be a lengthy process such as the event items storage NPC (with lots of prompts).