Conventional multi-engined airplanes have a critical parameter called Vmc - minimal control airspeed. This is the speed below which the rudder will no longer be able to keep you flying straight with one engine out and the other at full power. Get into an engine-out situation and let your speed bleed below Vmc and your plane will tend to "roll over and play dead." This is a bummer, especially on takeoff.

Some single engined planes with big engines also have a Vmc, especially if you hammer the throttle too quickly. The engine's torque can be more powerful than the ailerons and rudder's ability to counter it, so the plane will torque roll. Several of the WWII fighters like the P-51 Mustang had that problem, especially if a pilot got ham-fisted when doing a go around following a botched landing. If he was flying too slow and applied power too quickly, the plane was liable to torque roll right into the ground. Reportedly, this "feature" killed quite a few inexperienced pilots. The trick is to apply power gradually and let the speed build up so you can maintain control.

I've known of a few high performance homebuilts like the Polen Special that also had this problem. It wouldn't surprise me if the Firecracker has it, too.