the delay is not the time the servo will work but the time between the pulses
Are you saying you want to control the time it takes for the servo to travel from, say 0 to 180 degrees.
Or are you trying to affect the PPM frame time?
Can you explain what it is you want to do, so thennn maybe we can help you better.
(BTW, I don't think people use SoftwareServo much anymore - the current Servo library is more versatile)