Dippy, the motor I'm addressing is the common single-phase shaded pole induction motor, commonly found in small appliances such as fans, small aquarium pumps, portable heaters, etc. These don't have separate start circuitry.
You bring up a good point, though. Before applying a circuit such as this, it's important for the user to verify the type of motor that's used in the appliance. This isn't, by any means, a universal speed controller.
On another front, I've done some Googling, and have found that the voltage derates linearly with frequency:
<b>V = design V * target freq / design freq </b>
That makes programming simpler.
Thanks for your input!
Tom