I’d say that the seated cable rows and chinups would adequately tax the elbow flexors, whereas the DB triceps extensions are direct extensor work in themselves.
If you do feel like you need to add some work, I guess I’d recommend some incline curls (to hit the long head of the biceps even though it’s already getting some work with pressing; the short head is very active with chinups). Although there is definitely enough extensor work there with all the pressing and extensions, I suppose you could add something lower intensity; perhaps some one arm overhead extensions.
Again, I tend to think that you’d be better off without direct arm work as per Chad’s original program. Remember, the whole premise behind specialization is that you MUST be willing to sacrifice volume for other muscle groups to achieve the requisite overload on the lagging bodypart. Check out “Specialization Periodization” for more details.
I know Chad will have some excellent thoughts to add; this is just my take.