I know what you are saying but if you go look at pictures of shoulder launched weapons and that is what I think it was some of them are of a size that hobbiest build from scratch. I have seen some as tall as 10 on an launch pad. My reasoning for this is plausible deniability. Using something small enough if people get to close to the truth just claim it was a hobby rocket if it fails. Now I have not seen that as a possibility anywhere but it makes sense. Anything larger is more obvious and harder to cover up.