Stock FETs are 2SA1792. Four of them are used, two on the top of the board, and two on the bottom. Not sure if this is how the Mini-Z does it or not, I only saw stacks of two in the pics.
I posted on Mini-ZRacer about an idea to use much larger FETs instead of stacking the small ones (though I didn't say it was for an XMod
) and I still think this is the way to do it. It avoids the heatsink problem (Heat sinks would be attached directly to TO220 packaged FETs) and allows you to pass as much as 70A through them. Of course at this point, thicker wires will be needed, and traces on the boards might need to be beefed up as well. But the reliability of such a setup should be far better, and more cost effective. Such a setup would cost about $10 for the FETs (two each of N channel and P channel would be required), and a couple of bucks more for the board and wires, and would be the equivalent of having more than 10 stacked FETs.
I just need to order my parts and test this setupto be certain it works.