I've done GC at HArd level in at least 3 vehicles by now. One was the Dodge Ram with about 650 horsepower and at least 1 or 2 weight reductions (4,500 pounds). And I'm pretty sure I used either an STi or an Evo (423 hp...2,700 pounds) and maybe an Audi A4 (roughly 450 hp and 3,400 pounds, according to my notes).
I find it best to try and get ahead EARLY, because this means I have control. This means making a 2nd-gear launch in some cases, or whatever works best with minimal slipping. The launch has to be perfect. Sometimes, this means a full-custom gearbox setup, tho I've used super-close gears as well. Getting a good launch guarantees my car or truck will either pass the Ai or at least keep up with it until whatever turn happens to approach first. Although I try not to just slide-slam them out of hte way, sometimes it happens.

It's near-impossible not to pass without at least some rubbing of course.
Once I'm in the lead, I often try to keep to the
inside of all those hairpins, even if I wind up tapping the inside mesh a little. Brake as late as possible without sliding, and keep the front of the car pointed forward.
The Ai can't pass from the outside, you see, and they don't cheat via wall-riding, but they WILL slam us. If they manage to slam a front fender (because I've gotten sideways and allowed this to happen) it's usually a restart. The Ai has a habit of trying to slam or push us out of the way,
Personally, I find Ice Arena just frickin' 🤬 near-impossible in anything other than an actual rally car. I've tried various civilian models...

If Ice Arena is 10/10 so far as difficulty goes, I'd rate Grand Canyon Hard a 9/10, simply because I've managed to use non-racing cars to finish.