I think the analogy would be more like craft falling through the atmosphere. I found one NASA article that says interstellar wind speed is 26 km/s, which is four orders of magnitude smaller than .2c. Practically speaking I think you can model it as a constant .2c headwind.

> will be forced to apply rudder to compensate. These things have no rudders.

These things are pretty hypothetical, but I think the concept pretty clearly requires them to have something resembling a rudder since that's their only realistic means of attitude control.

Or, essentially they would be like people in wingsuits falling.