RE: X-29 Vertical Canard Placement/Stability Issues
The short answer is: Place the CG for stable flight, unlike NASA and users of other unstable jets - F-16, Rafale, etc. This is done on model jets all the time.
The side effect of this, is that the CG when placed for stable flight, will be farther forward than scale. So the scale location of the landing gear can put more weight on the nose gear and make it harder to pull the nose up on takeoff. If you have a model without LG, no worries.