Well.... actually the way I see it is that it only has to provide less lift than the wing does. For CG's behind a specific point the tail has to lift positive for all flight attitudes. But when it lifts harder than the wing does then we get into trouble.

I agree that for CG's forward of and slightly behind the generally accepted 25% point the stab will operate in a negative lift mode and for CG's a short distance behind the 25% point the value will float from postive to negative depending on the airfoil and other considerations. But once we get the CG back to the 35 to 40% point it's all positive. And for most free flight contest models the CG's are at least 40 % back. The P30 in my story has about a 50% CG or thereabouts.

I'm having an awful time finding it now but Mark Drela posted a great chart that showed a continuous progression of stabilizer sizing from very small to canard and how the lift on the "stabilizer" alters for a neutral point CG from negative for small % stabilizers to strongly positive for canards (obviously) with the large stab free flight types and tandem wings shown as well. It also strongly drew home the fact that a canard is just a very unique form of normal planform as far as stability analysis goes.