@Kyle Vanderstoep You might already be aware of this. To prevent custom fields from being copied using the Copy/Paste functionality, you can redefine the view as shown below and include PXCopyPasteHiddenFields(typeof(APInvoiceExt.usrTestField)) as demonstrated in the example.
[PXCopyPasteHiddenFields(
typeof(APInvoice.paySel),
typeof(APInvoice.payDate),
typeof(APInvoiceExt.usrTestField),
typeof(APInvoice.intercompanyInvoiceNoteID))]
public PXSelect<APInvoice, Where<APInvoice.docType, Equal<Current<APInvoice.docType>>, And<APInvoice.refNbr, Equal<Current<APInvoice.refNbr>>>>> CurrentDocument;