Paul,

Most Cap's pitch up when you reduce throttle on landing, or balloon, due to the high thrust line and low center of drag. To correct this you add 1-2 degrees of up thrust on the motor mount. The 1/4 scale Cap fly's great with 1 degree of up. Using a meter check that the wing is at 0 degrees, the stab is at 0 degrees and the motor is +1, 1 set of washers under mount on the bottom usually works.
The biggest problem people have with the Caps is the enormously powerful rudder and elevator, it's also its greatest virtue. The design isn't any more prone to "snapping" than an Extra, in fact they have virtually the same wing and the Cap has dihedral to boot! What it does have is an elevator and rudder powerfull enough to stall the wing at any time in any condition, regardless of speed.
Consider a stall being when the wing exceeds the critical angle of attack and stops producing lift. You can do it with pitch or with yaw. Example: During full throttle level pass, apply full rudder and the plane will tuck under in a violent snap roll. During a hard "bank and yank" turn, you apply too much elevator and it'll snap out.
The movement of CG effects the force required to induce these pitching and yawing movements. Like moving the fulcrum point on a lever.

If you keep the Cap light and make sure that it's straight as an arrow it'll be the most impressive flying plane you've ever flown. Most guys that fly them get hooked, you'll love it. Just ask Mike, we've both got the Cap virus bad.

Chris