I would say you should not use more than a cubic centimeter. I use just less than that. I probably use .7cm cubed (or close to it). This is by no means an exact science though. You do NOT have to be exact. You just have to ensure that you have enough to cover the entire surface in a very thin layer, remember this is not meant to fill a layer between CPU/HSF it is just meant to fill any small gaps in the junction of the two (you do not need a lot). But if you put on too much it is easily removed with toothpicks and teatowels... not a big deal (just kind of a waste of AS 5. You are taking this far too seriously just slap some on and give it a try, you will find that it wasn't worth all this worrying.
<b><font color=red>Go date P4man or something, bye!</font color=red><b>