I understand where you are coming from, but this has not been an issue so far for us. When we encountered a locked or nearly-locked rear wheel this was each time after a travel with the bike and in most cases before there was any SideWinder there. As to hauling around a bike on a SideWinder, the response from the current rack appeared completely elastic. I cannot tell about the long-term impact on the rivets, but the concern certainly adds to interest in strengthening the rack structure.

The SideWinder itself allows you to integrate pretty seamlessly with the rest of the population and, since I put it on, it has been my preferred way of rolling the bike. In fact if your concerns were true I would still persist in using the SideWinder or equivalent or partially equivalent contraption and, in spite of potential loading problems, either seek ways to strengthen the existing rack or switch to another rack, down to making a rack from scratch.