Ok, that´s why i decided to design my own board...
mosfet outputs are mostly a problem (for example low quantity and of coarse heat issue)
problem of nearly all that stuff is buy cheap, get cheap.
well designed circuits usually increase cost.
starts simply on voltage regulation , needs a kind of driver for the mosfets , good quality connectors
and so on...
so i think for you it´s best to follow the instructions in second link you sent.
(but take care , due is very sensitive on voltages >3.3V on I/O Pins.
also supply voltage of 12V is not the best for due.... should be around 9 V)
up to now i fried 4 of them by testing in hurry...
kind regards and good luck doing the mods :-)