Slash 4x4 with HV-Maxx

So I'm considering picking up a slash 4x4 roller off of Ebay. I have heard that it is possible to run the HV Max 4.5 off of a lower cell count. What would I have to do to my HV Maxx so it could take this lower cell count and how much modification is needed to drop it into the Slash 4x4?

[Arct1k]

Just to wire it for a single pack which novak shows you how to do and run it on 2s...

Worth adding the heatsink / fan as it still runs a wee bit hot...