Offset Crank Pulley

So I read that if you have a symmetrical pulley for your car and you need one that is offset, you can just oblong the one hole and it will work. I have read plenty on here of guys doing this but my friend swears it's a bad idea to do. Not saying he is wrong, or dumb. I like to do things the right way too but has anyone ever had any sort of issue when doing this and driving their car? I just need the reassurance lol.