i have 205/45's on 17 x 8" wheels, so same width...stretch is there, but nothing outrageous...i had more stretch with 205/40's because of the sidewall being smaller, but wasn't in to it overall (those tires were on sale in that size; only reason i bought them)...
however...before everyone else says it...a 205/45 on a 16 is under sized, you'll shorten the final drive enough that 3400+ rpm at highway cruising speeds will be normal...