Since the (telephone) CSR did not seem to know, thought I'd give
the Penfed e-mail contact a try:
Q: How many external transfer accounts does Penfed allow me to have?
A: Thank you for contacting Pentagon Federal Credit Union.
Our IT Department has confirmed that we can hold up to 430 entries
for external accounts per member PenFed Online profile.
If you need further assistance, please contact us.
Pentagon Federal Credit Union