i have not been on any of these boards forever . . . i was looking for some info on after-market shocks for a lowered p5 when i saw this string.
there is a combination of size components that need to be matched up to lower and get no rub: rim diameter, rim offset, tire width and tire aspect ratio. my point is that it is more than diameter being close to stock (which is important to keep the speedo etc. close)
ultimately i can tell you that you can (i do) run a 215/45/17 tire on a lowered p5 (i have eibachs) if you get a rim with a high enough offset (at least +48) with absolutely NO rubbing with a full load.
i think you will have problems with the 45 series 205/17 and +42 offset. the +42 will not move the wheel into the wheel well enough to clear the fender. go with a 40 series as the other members were saying and you should be fine.
Cheers, Mark