Heatsinks for DoZ

[ultrachrome]

I purchased a pair of 2ft long sections of an Aavid extrusion from www.meci.com and I'm trying to determine how much I need for a DoZ amp.

The Aavid doc specifies .8 C/W @ 3in and ESP recommends a heatsink of 1 C/W. Does this mean I only need 3in of heatsink for each channel? Or is that each device?

Using ESP's calculation, Thermal Resistance = 50 / sqrt(Area). With standard to metric conversion in mind, that calculation results in 4.4in long heatsink.

Based on what I have seen with Pass's Zen amps and specifically one builder's Zen v4 that uses the exact same heatsink, this doesn't seem like enough.

At a minimum, I intend to cut the pieces into 8-12" sections. The tower look isn't that appealing.

Thanks.