I am not familiar of your type of airplane, but I do know a thing or two about "wanting to increase payload". Increasing the payload requires you to increase the engine size as well as prop size. The more number of prop blade does not increase performance but versa. Generally, 3-blade used in rc is mainly for scale looks (with some speed sacrifice). 3-blade generates more drag on the engine and more turbulence at the prop, because the blades are closer together. For example, a 13X8 3-blade will move your plane slower than a 14X8 or 13X7 2-blade given that all are mounted on the same engine and plane.

Increasing the payload also means increasing wing loading; therefore, the plane is more challenging to fly. Depending on the type of airplane you are flying, for a 60 size, you can increase the load by 3lbs and still can take off, but you must increase the engine size to 90. The heavier the airplane, the more runway it needs to take off and land.