yeah, you're only going to want to have one BEC hooked up. Also if you've got a fuse on the tail motor, make sure to put a switch that can handle more than the fuse. Those tail motors can draw up to about 7 amps on the stock battery in a stalled condition. But you're right, probably only about 2 amps max in normal, or even 3d flight.

As a side note you may also want to get a switch that fails in the closed position, although that may not be that big of a deal for you.