Most put their radio box in one of two locations:
1) under the cockpit with a driver on the lid
2) aft of the motor on the left side of the engine bay.
Since you boat is electric, you would really need to make the engine bay waterproof(as much as possible anyway) since you don't want water to get to your electronics. A radio box wouldn't really be needed as much as it would in a nitro boat since a nitro boat needs to get air to the engine to get it to run as well as room for the tuned pipe, hence to two preferred locations of said boxes. Now, as for your adding a bulkhead, yes, it would do the job. The catch is that you install some way to keep water out of the engine bay. A recessed platform with lexan that you can tape down would work, for example. I'm sure others have different ways to do so as well.