Defaulting Payment Terms on POs

I know that Payment Terms normally default on PO's from the vendor master, but I have a couple of questions:

1. We have vendors with VN and OA partners defined. Is there a way to have PO's defailt payment terms from the OA partner instead of the VN?

2. We have some PO's created from contracts and in those cases, do payment terms default from the contract instead of the vendor master?

Thanks,

Rick