I've done 16's on a beetle (with 225/55R16 tyres) and it was a phenomenally bad idea, but there are people out ther ewho go even further. Personally i'd suggest you do what you feel like.
However i'm going to go back to origianl steel wheels (with hub caps) with my 1303 so if you go for ris on your car let me know, i might be interested in buying your originals off you.
Personally i'd advise you to resist the temptation and stick with stock items.