[Amps] attaching a heat spreader to a heat sink

[Dan Sawyer]

All,

I am building an EB-104 kit. My question is: What is the best way to 
attach a copper heat spreader to an aluminum heat sink? My plan is to 
lap the surfaces on a precision granite machinist block and then use a 
very light coating of thermal grease. The surface will be about 4X5 
inches. I plan to use 4 screws about an inch in from the corners. The 
transistors are near the center, I will use longer mounting screws and 
rely on them to hold the center.

Is this correct and sufficient?

Thanks - Dan