Shippo Reference Field Not Applied to USPS Label

Question

I'm using the Shippo API to create USPS labels, however, when I use reference_1 or reference_2 fields in the shipment request, the custom strings entered are not visible on the label.

We use those fields for the order number or rma number.

"extra":{
    "reference_1":"Order Number",
    "reference_2":"RMA Number"
}

Are those fields supported in that way, or should I be using some other field for that purpose?

Answer 1

I actually figured it out. The reference fields are at the shipments root level in the newer version of the api docs.