Thanks, all. Fidelity to the available references was my primary goal with this. Still and all, one gets into some guesswork and making choices based on intuition.
One's first inclination is to think of it as a just-relaunched vessel and therefore pristine, like the ST:TMP ship. Starfleet keeps the plastic wrap on their lampshades for twenty years or so.
The TMP ship has a great deal more surface detail, however, than the TOS ship and all of the pre-movie treatments of this ship looked similar in detail to the TOS ship. So more aging and weathering along the lines of the TOS ship is helpful.
The TOS ship also had more windows. Jefferies' drawings were pretty specific about window placement on most of the Phase II ship, however - the exception being the saucer.
Andy Probert has a page of photos of the Phase II vessel under construction: