I have some questions before I can accurately model the board:

1) What is the thickness of the silicon?
2) What is on the under-side of the board?
3) How are TerraHash, yourself and others expecting to transfer heat from the components, through the silicon, to the aluminum heat sinks? Thermal pads, paste?
4) What material covers the avalon chips and why can't heatsinks be attached directly to them?
5) This is only a single layer board with no trace or components on the under-side or internal layers?