A proper PT-era Cushing makeup ought to be rather less gaunt-looking than the Tarkin of 1977.

Here's Peter Cushing as he looked in Hammer Studios' initial 1958 Dracula:

Contrast this with Cushing's appearance in Dracula AD 1972 (no prizes for guessing the year it came out).

Cushing's extremely angular look in SW 1977 was in large part due to the physical strain of his grief after his beloved wife died in 1971.

As I recall, in his autobiography he even admitted that he tried to induce a heart attack in himself through overexertion the night she died.

This is a rather ghoulish subject, I'll admit, but if you're going to have the audacity to create CGI Zombie Peter Cushing, then as far as I'm concerned you don't exactly have a leg to stand on in the decency department.