I have kept Rummynose with somewhat large (?) adult angels in the past--angels with bodies about the size of a dollar coin?. No problems at all--rummynose can actually get pretty big and they are very fast swimmers. I have never seen any aggression from Rummynose towards anything.
IMO, Angels and Rummynose should be fine. I agree that the Rummynose should ideally be in the tank first, though. Unless you have a tiny angel, and are hoping to raise it to maturity.