If you put fins on a rocket that are .01" tall, CP becomes N/A. If you make them 0.1" tall, CP calculates normal (assume there are other fins, these are not the only ones).

Here's the Simple Model Rocket example with a set of these fins.

[short_fins.ork.zip](https://github.com/openrocket/openrocket/files/14809281/short_fins.ork.zip)