In structures with a small radius, the "gravity" differential between your feet and your head is a bigger issue than the Coriolis effect. Large structures using the tether approach produce sufficiently large forces on the tether that it becomes a significant engineering problem. Tether structures also suffer the issue that they are much harder to stop and start than a ring structure. This is important because you do not want the structure spinning whilst you make course adjustments. There are modifications to the design that compensate for this, but they add significant complexity to the design of the ballast.

The ESA have put a lot of thought into this, as have Rosmoscos. I assume NASA have put a fair amount of thought into it as well, but I've nothing to back that up.