ORIGINAL: twomanytoys
I would highly recommend against mounting a receiver outside the battery box expecially on teh side. It will leave it open to damage and possible runoff.
+1
If enything, mount it along the centerline as much as possible, even above the mid-mounted tank (I asume you are doing a mid-tank mod). Even though your electronics might be exposed to rollover damage, at least roll overs are not as common as side-swiping stuff that normally happens on a basher.
It is possible to mount your RX and batt up against the front shock tower to help minimize their exposure to even rollovers.