i run SD200's in planes, not 46 sized, but those tiny cogs seem ok.
what you have is a 2kg servo ( if i remember that newton stuff right ) i would replace them with 3001's
leave one on throttle, as for weight, try a rudder pull pull and have that servo in the body near the wing somewhere.

low weight is a good idea, but the SD250 would be tight on power, think Hi-tec do some hi torque minis