Flexfields transferring to Credit Memos

Hi.

We have a user defined Flexfield at the AR Invoice Line level that tells lets us choose which lines to print when an invoice is printed.  Our invoices typically have hundreds of lines and we only  need to print about 5.

However, when we issue a credit memo against an invoice, the data in these flexfields are not transferring to the Credit Memos.  I assumed that they would.  Am I wrong in thinking that is the intended functionality?

Thanks

Katie