If you have a Cusader II you are replacing you could convert the SEM servos to rotary encoders if you want to go that route? That might be easier...The SEM's use a 5 mm stub shaft on the tach side of the servo....pull out the stub and put in a longer 5 mm drill rod and use USDigital encoders or some other brand. They are about 50.00 each for the encoders...make new end plates to mount the encoders and go that route.....