ok guy this is what i got the instruction book has two CGs one is 67mm the other is 80.5mm so what I did was used a MAC calulator to figure the CG I have a wing cord of 9.5 and a wing span of 55inchesI punched in the numbers and came up with A CG of 2.66 inches that number falls in between the 67mm and 80.5mm by the way I like to use 25-28 mac as a starting point so what do you all think michael