150mm, that's about 5,9 inches, it's where red meets yellow on the wing.
You can check your CG by flying a 45° upline (crosswind, so that the wind has no effect on your upline) do a half roll (invert the plane).
your plane should now keep on flying the 45° upline or descent a little bit without elevator input.
If your plane goes up, the CG is too far backward, if the plane goes down, the CG is too far forward....

keep on flyin',

Gr Gaaaz