Heat sinking Gecko’s

Hi all,

I have some 5 amp steppers and Gecko 201's

I was wondering just how much heat sink is required.

What I would like to do is mount them on a 4"x4" x 1/4 aluminum plate
on my floppy holder in my old PC case and have a fan blow across them.

Some of the aftermarket heat sinks have some pretty heavy fins.

Any words of advice ? cautions ?

Dave