These Skyline discussions make me interested. I have to solve my CSP probs, so I can do some test laps with the Skyline, too. I cannot remember having such tire temp trouble during my preseason tests for the car choice. But I did only very few laps, so that's not representative.
About the Caddy I can say, I had never tire troubles. Either with temps or wear, it was always ok. But I know, even Greg was often wandering about my lower tire temps when we did some training together. But I cannot say how I got them, as I did nothing different than for other mods. Maybe it's the car, or the driving style or the general way I setup the car. My temps where always around 110 at the front and 105 at the rear. Seldom, I got short high peeks up to 116 at the front in a corner. And that was quite perfect for me as the car felt best with tire temps between 100 and 110 degrees.