There's a pretty good series by GI on how to set up your BW mosfet:
I can imagine the mosfet will never perfectly count the shots fired as it does not have a BB sensor (it just makes an estimation), but it should do the job.
And thanks for the tips, I'll just send them an email about the 3rd version and check if it is real steel ROF only.
EDIT: never mind, it has all the same features (source: http://www.aegwizard.com/Home_Page.php)