Introductions take a lot of time. Spook and Remus have been together for almost two years now and they still hiss and spit at each other from time to time. Cats are just that way. Be patient, as cats develop a very protective attitude about themselves especially when they've been forced outside.

Things will get better, and Cubbys willingness to be tolerant even while being held is a good sign. Introductions go easier when at least one party is mellow!