I think if it comes down to bonus seconds, Aru won't beat Dumoulin in a sprint to the line on any of the remaining stages.

If Aru and Dumoulin aren't sprinting against each other for those bonus seconds, it means one of them is far enough ahead/behind the other that 4",6",10" don't matter.

I think Aru's best tactic is to try and use Landa et al to distance the big guy on the climbs and hold enough of a lead on him on the descent. He may get help from Purito. He'd have to offer Quintana/Valverde the stage win to get them to pitch in.

The other thing is we don't know how Dumoulin is at descending. Judging by his ride today (and in the Utrecht TT in the tour) he can handle his bike around corners. Can he do it on a road bike in an aero tuck at 80-90kmh?