Well you have some information that is correct but some of it is not. First of all the 235 / 20s are in fact 8.8 inches wide in terms of their tread. But that isn't really the crucial variable it's the section width. I'm not recommending a 10in wheel for that tire and in fact if you read my prior post I would say a 10 inch wheel is a stretch fit on that tire at 9.5 in of inches of section width. When you say the 235 / 35 looks about right on an 8.5 inch wheel, are you aware that most folks who track the car or who do autocrossing or racing would argue that an 8.5 inch wheel is not wide enough to get Optimum performance from the tire? A wider wheel that is at least equal to the section width is generally deemed as the optimal solution to keep the tread patch square and resist rolling up under cornering forces. Now that has other downsides, chief of which is that the wheel is more exposed to curb rash. But like everything else it's all trade-offs. If you want the best performance at least get your wheel width to be equal to the section width of the tire. That's section width not tread width
I was speaking strictly to the looks. I'm sorry if that wasn't clear. Lots of different considerations when looking at street v. the track. I won't argue about the track stuff but taking a look at a track oriented car like the new ZR-1:
Wheels are 19x10.5" and 20x12."
The stock tire sizes are 285/30/19's and 335/25/20's.
Section widths are 11.4" and 13.5" and tread widths are 11.3" and 13"
The people buying ZR-1's are mostly likely going to have a dedicated set for the track, though. Maybe they'd get wider wheels (all other things being equal.)
The GT3RS also runs larger sectional widths (about an inch wider) than the wheel width, front and back.
My tire installer does a lot of work for the car club members in the area and tracks his cars as well. He recommended staying in the middle of the recommended wheel width range provided by the manufacturer of that particular tire (whether it's an all season for the street or a sport cup2 for the track), and if anything, err slightly to a wider wheel for the track (as you stated.)