It seems that most people make a waterproof area for the radio/motor/other electronics separate from the rear, where the running gear, servo arm, and such transitions through the hull. This wood kit that I'm building has lightning holes through nearly every part of the boat except the back. I could easily make a waterproof section in the rear 6" or so by just adding a bulkhead. Does this fulfill the intent?
I finally came up with a way to support the rear fins/stabilizer/whatever it's called. Still needs a little adjustment, but it seems to work well, and it was under $15. Also have a nice amount of adjustment on the horizontal stabilizer. I don't think the binder clips will work for 50mph+, so those will be replaced with screws, probably plastic screws so they break instead of the tail pieces if I crash.
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.
Not a lot to update but I have made a little progress. I've been doing little things to get ready to get the decks on with the idea I'll never be able to get access to that area again without cutting things that I don't want to cut. Internal hardware for the front wing, turn fin, and such. Finally, I got the STBD deck on today. I've been using CA for most things, but I decided to use epoxy this time. I like CA better because I hate waiting. It took everything I have to not take the tape off and start sanding, but I managed to wait. I'll give it 24 hours.