I built it last night. I decided to go with the spring loaded timer so that I could adjust the amount of time the power heads would be off. Also, I can turn them back on right away by winding the timer back to the off position. I didn't know if this could be done with the 10, 20, 30, 60 min., and hold timer.

Easy to do once I figured out the wiring. (It's a little different than what Bill describes in his thread.)