I'm pretty sure the A2 and A5 are equally rated, the A5 just being a larger frame. That accommodates a stock drop in installation versus hiding the A2 more easily.
I just put the A2 in an ATV, used the supplied foam pads to take up the extra space, and snugged it right up. Click-crank-vroom! Left the utility pigtail installed for off season charging. Love these things...