If we then add a few conditions: "no links in the root message" and "OP may not be the first to comment within some unspecified amount of time," that could make it even easier to limit CSAM.
You'd need to make the individual carriages long enough and/or place the coils close enough together for the carriage to always be supported by at least two coils. In such a case, it'd likely feel like a pitch oscillation. Like being rocked back and forward, fairly little and very quickly.
Wish the poster will step on a Lego twice this week.