Would handling be really that bad? 17x8 rim with a 255/40?

I know my rims are a 1/2" undersize, but $99 for Hankook Ventus V12 EVOs in 255/40-17 from TireRack is looking very attractive! I've always liked the more meaty tire look. I don't track the car, just some spirited drives once in a while in the mountains. I just see so many different opinions. There's a lot of Mustangs, STIs, & EVOs happily running 255/40 on the stock 17x8s with no issues. Any folks here running this rim/tire combo?