Ok I just looked at the whole thread and dont see a link to your "h-bridge" so please post a LINK.
As for reverse emf etc then until I can see what you think I can see then I cannot answer.
The crowduino is pin compatible with regular UNO's etc so if it is a shield then you should be able to just pop it right on top.
EDIT... My apology....Yes that one will drop right in and has its own supply terminals so will not be an issues with back emf etc.
It is also quite beefy as these things go and has a little wiggle room too with up to 20 volts and the extra amps.