Check this thread for a similar plane:
http://www.rcuniverse.com/forum/fb.asp?m=9511096
You can do the same graphical calculation and locate CG at 25% of the total MAC formed by both shapes of the wing planform.
I don't know the exact dimensions of your plane as to do an exact calculation following this method.
However, I have used the plane of the link, which I scaled up to have 320 mm of chord at the wing root.
For that setup, the CG should be at 107 mm.
Please do the calculation using the actual dimensions of your model in order to determine the exact CG location in your case.