Oops, I just saw the X29 bit.

Yep, use the MAC calculator to find the MAC and then you're looking at 15 to 18% CG.

Also with a swept back wing you washout the tips to give you the stability you require. As a side benifit it tends to reduce tip stalls when turning at lower airspeeds or in high G turns. A swept forward wing isn't going to be so tidy. For the tips you'll want regular lifting sections but for the root you'll be wanting a strongly reflexed type of airfoil to generate the proper lift progression. You may even have to build some washIN into the tips.

This is why you don't see many strongly swept forward X29 style flying wings.