Lets get honest
Lenses are NOT manufactured to give their best performance wide open -- but stopped down 2 or 3 stops.
That;s just a reality
Further you are looking at a zoom, which is also not designed to give it's est performance at the wwide and long ends but in the middle. These are compromises, lenses of convenience, not sharpness.
So you would do best with a prime that is a couple of f-stops wider than what you need like an F 1.4 or 1.8 shooting at f 2.8 or 3.5 - 4.0
There's no cheating physics
and "micro adjustments" don't exist on the 60D, neither will they necessarily help