DON'T DO IT ! 138 mm is still WAY OFF , .....look I have spoken to CMP and what they told me is that all of there 50 size Zero plans / manuals are suppose to refrence the larger 71" 120 size Zero wich you now have , and that it lists the CG at 95 to 110 from the LE , I own the 50 size wich I had to balance it at 75 to 85 from the LE , and it flies GREAT ! so you see the instructions you and i have for the 120 size zero is actually meant for the 80" wingspan model , SO the balance point for the 120 size is 95 to 110 mm from the LE , no matter what 138mm is almost 5 1/2" like i said before NO WAY that right ! ....... just my two cents worth