I have absolutely no data, just a gut feel and some common sense. Your van is not going to fall apart or explode from a tank or two of B20. If you're driving through MN and need to fill up once, I'd do so and not worry about it.
If you really want to be careful, fill up on B5 before entering MN. Then at about 1/2 tank top it up with the local B20. That should get you an average of B10-B13 in your tank. Once out of MN, fill up at the first opportunity with B5 or better. That keeps the B20 diluted and closer to the preferred fuel.
My thinking would be considerably different if you lived in MN and had to consistently use B20. In that setting, I'd be looking for a diesel vehicle that was OK with a steady diet of B20. Or I'd be looking at a gasoline engine.