Your statements are a bit confusing- A trike gear has a *tough* time nosing over unless the nose-wheel is turned sharp while on a high speed roll. Nose-over is possible on a tail-dragger if the man gear is to close to CG etc-

The CG machine is as simple as it gets when it comes to balance point- The only real issue is in the actual application of it (but that's up to you) Its not a perfect machine but the human factor is usually a good place to start when problems arise.. *RTM*

For troubleshooting I would start with the takeoffs- if both planes exhibit problems during roll-out, and both problems are similar than look at your nose-wheel setup (is it to sensitive)?

My friend always used to flip to the left because his thumb would flip the throttle slightly left while throttling up- took him a year to get it under control...