Hey ann,
What's the width, 5 inches? Since you wrote "&.5" I'm guessing you ment to say 7.5" considering there are probably almost no 17x5's.
If it is 5" wide that's a bit skinny, but will work you just might need to adjust with wheels spacers or something to look good. Also 205/40/17s might be a big wide on a 5" wheel.
If you ment 7.5" then you did a great job! that's my personal favortie wheel size. 205's are a bit skinny on that wheel though. The only bad thing about that is if you hit a curb, or slightly touch one you will screw up your rim cause the tire doesn't hang over at ALL for extra cushion. Some people like the look and some don't as well. A 205 tire on a 7.5" wide wheel will be the the least extream you could considered a tire "Stretched" on the wheel. It'll give great handling though.
Here's the only example I could find:
http://www.rscosworthbreakers.co.uk/...loys%20004.jpg
You can BARLEY tell, but from the side it's more obvious.
Here's a better example, this would be like a 215mm tire on a 7.5" wheel:
http://upload.wikimedia.org/wikipedi..._s13_wheel.jpg
Stretching tire's is popular among drifters and on the rear of VWs