Don,
I have not tested it with the rigid speed controller, but it should work. There are two ways of doing this:
Method 1:
1. Open the router and measure the impedance the current pot is using.
2. Use this guide for selecting a parallel resistor so you can set the total impedance of the circuit equal to what you currently have.
http://www.cnc4pc.com/Tech_Docs/Replacing_pot_guide.pdf
3. Then proceed to rewire as you described.
Method 2:
1. Get a commercial speed controller, like this one:
http://www.harborfreight.com/cpi/cta...emnumber=43060
2. Replace the connections on that speed controller, which is a proven thing.
You could leave the pot on the speed controller and use it override the speed been instructed from the PC, but keep in mind that if you do that you would only be able to reduce the speed to ½ of what you normally would.
Thanks,
Arturo Duncan
http://cnc4pc.com