Can swerve be eliminated with an above-center hit?
The closer the cue is to level, the less a shot with english will swerve. Unfortunately, because of the height of the rails, the diameter of the cue (above the rail), and clearance between the cue and rail, the cue will not be level on most pool shots. Also, if you hit above center with english, the squirt direction is down a little; so even with a level cue, an above-center hit still results in slight swerve action (because the effective impact direction is still down a little).
Having said all of this, an above center hit can reduce cue elevation and reduce the effects of shot speed and ball/cloth conditions (i.e., there will be less swerve).