If you are ready to shop for best performance and best safety private aircraft, what characteristics will your aircraft feature? What type of propeller will you use ? These considerations will affect the aircraft aerodynamic propelling efficiency, flight control maneuvering configuration, flight safety, flight speed and performance; effect to vibration and noise and the most easy catchy specs, fuel consumption, and flight range.

What's the problems of current propellers in private aircraft market?
Current single engine private aircraft commonly use single stage dipole low cost props, which have lots of problems:
Propeller torque effect makes pilots busy to trim the aircraft to keep straight flight when taking off, or when accelerating. The aircraft tends to roll following the prop's torque.
Propeller torque makes the aircraft unstable when flying at variable speed. Propellers are often set to constant speed RPM to minimize torque effect.
In case the aircraft stalls with lost power, the pilot has difficulty getting off stalling and leaves himself in an extremely dangerous situation, due to recovering the engine and props speed will make the aircraft roll further.
Single stage propellers are low thrust. To produce sufficient thrust for accelerating speed, propellers often spin on allowable max-RPM. That makes the propeller blade tips spin near the speed of sound. Thus the shock wave makes a very loud " bra-bra " explosive noise and serious vibration occurs on the propeller.
Due to low thrust, single engine aircraft consume high fuel cost, carry less payload, and serve shorter flight duration and range.

Propeller Reinventions
Based on aerodynamic theory, 2 stages propelling produce more thrust than single stage propelling. 2 stages propelling makes better thrust acceleration.
Coaxial counter rotation dual props can offset each other's torque.
In order to integrate and gear the 2 stage counter spinning propellers together, Linn designed a symmetrical on axis micro gearbox to gear the twin counter propeller together.

Benefits of this coaxial counter rotation 2 stages twin propellers :
Super efficient aerodynamic propulsion. Converts more thrust than single stage 4 blades propeller under same engine power. Produce a lot more thrust than a single stage dipole prop.
Working under lower RPM still obtain sufficient thrust to power given aircrafts. Thus, much more quiet, significant noise reduction.
Offset destructive torque. The anti-torque coaxial propellers can work at variable speed, and accelerate/decelerate the RPM speed at any time. Pilots feel free to accelerate the props and make easy straight flight without trimming. Pilots can maximally maneuver the aircraft to obtain advanced performance.
Fearless recovery control, in case the aircraft stalls with temporary lost power. Pilots can simply accelerate the prop speed to make straight flight off the stalling.
More thrust from same engine power, means capability to carry more payload, consume less fuel, longer flight duration and longer flying mileage.
Most ideal propulsion props for GPS guiding precision flight control mission UAV !
Likely a future propeller new standard for General Aviation.