Printing Labels to Printer Size FBA in Inventory List and not in Shipment Flow

I’ve got an issue that’s driving me nuts. I like to label my items being shipped in via FBA even when it says a label isn’t required so I can protect the item and put a label on the outside when the UPC isn’t visible. I’ve posted that question before and someone alerted me to say that you can print a label whenever you want from your Inventory Management page via the drop down next to the individual listing. The only problem is that avenue doesn’t allow you to customize the paper size. It’s all preloaded full page options. I use a rollo printer with individual labels and use 51mm wide x 25mm tall.

Any idea how to customize?