My opinion would be to build in right thrust per the designers specifications...If they say none..Then that is what I'd do...They may have done things aerodynamically which take care of the need for adding right thrust... (nice)

To add to the discussion:
There are several forces acting on the aircraft which tend to yaw the aircraft to the left while at high power setting and high angle of attack...P-Factor, Torque, Propeller Slipstream Effect and Gyroscopic Procession are all kinda acting in unison...(These forces act on the longitudinal axis (roll) under the same conditions)

P-Factor remains the same weather the aircraft is upright or inverted and climbing...Now when the aircraft is upright: The pilot will add Right Rudder to counter P-Factor...However when the aircraft is inverted: Left rudder is applied to counter P-Factor...As a buddy once told me (a Pitts Pilot)..."If your pullin' on the stick it's right rudder..If your pushin' on the stick it's left"

Have Fun...

Chuck