I have a Swallow 90 ex ( 3.700 gr.) with an Mvvs 90 pooling in front I used a 14X8 apc Prop for the first flights , with that combination the model flays very nice and accurate but when full throttle is added its getting a little bit fast , also the vertical performance is very good but not the kind that you want for prop hanging as the model actually tend to accelerate at full throttle in vertical and it don’t produce the wanted torque if throttle is 60 to 75 % . It looks to me like a prop problem and I am thinking to change the prop to 15X4W apc .

I need your advices,

Has any body tried this combinations 15X4W apc with a powerful 2 cycle 15 cc motor.