Gunderson,
I have a standard bodied car but it might interest you to know some experience with 17" wheels. I too changed from these to downsize and don't regret it, the car is much more agile but grip I found reduced until the car was also wearing soft tyres.
As to the 17" I personally found that until you had gone round at least one corner with them they were a liability. Once done however they were fine. Question for you is, was this the first corner you had gone round (early in your drive perhaps when cold)?