ORIGINAL: RichardGee

Bumblebee... WELCOME to the fascinating world of piloting a scale Gee Bee R2

It is difficult to give you exact advice designed to cure your issue.... FIRST, are you positive that the following are PERFECT??

Dihedral - minimum 4.5 degrees each wing and EQUAL
CG - 17-18% of chord? This equates to 73mm - 75mm back from the leading edge
Minimal rudder throws - the rudder is VERY effective on this plane
PERFECT rudder linkage with NO SLOP
Digital servos w/minimum 150 in. oz. torque
Aircraft is trimmed for hands off, level and straight flight at 3/4 throttle
Flying wires are ''guitar string'' tight?

Your engine, prop and weight are perfect, but the extra HP will indeed add some P-factor. Compared to a DA150 the affects will be minimal.

Once ALL of the above are confirmed, you MUST mix some right rudder with your throttle. The total amount of rudder throw from neutral is about 2mm. The rudder should NOT begin mixing until you reach approx. 50% POWER... at that point, the rudder should mix in a linear fashion until at full power you have 2mm right rudder deflection.

Assuming you get all of this correct, you will likely find that flying this airplane IS a continuous compromise. As Delmar Benjamin confirmed, it is UNSTABLE in PITCH and in YAW. Correcting this required an expert pilot sitting IN the cockpit sensing every deviation... we on the ground do not have the ability to sense subtle changes.
A GYRO would be a great addition, but simply adding a gyro will not fix the issues unless you have the gyro perfectly tuned to offset the Gee Bee's tendencies... this will take trial and error... and the by the time you have it dialed in, you will be an EXPERT Gee Bee pilot and may no longer need a gyro