David, you are right in saying you just need to move the OTA if the balance point is towards the primary cell if one OTA is lighter than the other.
There are many OTA's that have the COG (centre of gravity) heavily set towards the primary cell. The Takahashi Mewlon is one such instrument. And this is not a problem, so why would it be a problem for a CF instrument? (this is a rhetorical question
) Why would this be a problem between a steel tube vs CF too? Now if this is just a comparison note from someone, then that's how it should be taken and not as meaning one is "better balanced" than the other because this is nonsensical.
Just remember, I am not advocating the use of black CF. My comments above are wholly about mechanical aspects.
Alex.