Well I got to think on (and play with) this all day, and I think my initial reaction to "oh no I have to deal with ice mode" was overreaction. There's a few layers of analysis here, not sure what order to put it all in, and I'm trying to avoid my tendency to get really long-winded
. But the bottom line in my case I think is:
An additional major contributing factor was front pad fade on the XP8s, even on my street tires. When the fronts start fading, of course the bias goes to the rear, which helps kick on the ice-mode.
Based on that alone, it would seem like it would be best to up the fronts to XP10 (at least) and get my brake ducts finished, which should lessen both the fade and bias contributing issues.
But, a major contributing factor to the pad fade (well, aside from lack of ducts) was that I was carrying around a lot more speed due to some skills improving, but I was abusing the brakes way more than I should have had to. We corrected some of this today, and I was able to make even faster lines with less brake abuse, and it helped a lot. I still got some ice-mode late in a hot session, but I was able to modulate through it and come out ok, and after pushing through that barrier for a bit, the XP8 front pad fade of course starting becoming increasingly obvious.
So really, learning to use the threshold better (so I'm not dipping into ABS in the first place), and not abuse my brakes in ways that aren't even warranted will go a long way towards fixing this for me on a practical level, although the ducts certainly can't hurt as well. Even then, I'm still going to be pushing the limits of the XP8's on street tires, but I think trying to upgrade the pads too far against these tires is probably a bad idea (just going to be a lot more touchy and sensitive on the ice-mode line when it does hit it), and I also think I haven't learned enough of the limits of these tires to consider upgrading to slicks either.
Really, where that leaves me for reducing the overheating problem is I need to not go balls out on the straights. If I held back at say 70% throttle on those long straights instead of flooring it, I wouldn't have as much speed to shed, and the braking system and the tires would all line up with my driving skill in the corners and work properly. In other words, even my lowly NA V6 really has a little too much power on tap for an ideal learning environment at my level of skill, if I want the rest of the system to hold up to a long session.
One way or another, I can play with modulating through the fade + ice mode and/or reducing my straight speeds and mitigate the ice-mode while continuing to learn how to push these tires to their fullest, and then consider further true tire+brake upgrades later when I'm ready, I think. The ducts will go on ASAP though