If your plane is certified to fly in RNP-10 (very popular in Boeing), in my modest oppinion you donīt need to say anything at all.
I'm not really sure on this as I don't fly RNP-10 oceanic airspace and neither are our aircraft so equipped. As far as I understand is, if you don't have an FMC to generate an FMC position from the IRSs and the GPS then you cannot be RNP-10.