My eye says that the LE of the wingtip will be really far forward, but it's hard to tell from the picture.

What you want is also going to depend on the airfoil a little, and don't forget to adjust the aileron reflex during flight testing.

For a starting CG, I'd shoot for something close to 25-30% MAC, which you can easily calculate.

Is this your first SSC plane or just your first own-design? If it's your first SSC plane, get someone to throw it for you, and give it a good shove, and be prepared for the plane to possibly loop over or nose-dive, it doesn't take much of the elevator trim to be way out on a new design.

What's the wing area?