I just tried it out and did a 1:20:xxx and that was with a couple of mistakes, so I have to disagree, 1:18 is definitely possible. Keep in mind it's an optimal lap.
But then I think the target times are too close together, and too far from optimal.
For example: 1.28/1.26/1.25 ------(huge gap)------ 1.18 (optimal)
Should be: 1.28/1.25/1.20
or add recognition for getting within a second of the optimal time for each event.