Have you considered hard luggage? It'd be vastly superior for the mission you described, and you can easily get away with one of the Givi E36 or E45 for 130-140 bucks. The VStrom already has a great mounting surface right on the back. Waterproof, lockable, robust... Throw any old bag you want in the back, and you'll be set.
That's my preferred setup for getting back and forth to campus, and it also allows me to lock all of my gear to the bike.