It really does not work well. I had an inboard many years ago I blew up, wanted to finish the season so I stuck an outboard on it. It might work better with an electric because you can shove the batteries all the way to the nose to get it to balance properly. Most of the time you end up with the CG way to far back for the boat to handle properly. The other guy was right back in the 80's people did try outboards on everything, found out they don't work that well, now it's pretty much tunnels only for outboards.
What can I say if it really worked well you would see more of them. My boat went from one of the fastest 3.5 monos in the club with the inboard to an also ran with an outboard.
For a scale play boat you might get acceptable performance, for racing it is pointless. The boat end up too heavy by the time it's balanced.
Tunnels are designed to operate with an outboard, and have you ever seen how a tunnel runs until it get air trapped under the hull and it gets up on plane? not too impressive, A tunnel is way harder to set up right than any other type of boat hull.
Been there, tried it with a nitro boat, couldn't wait to get an inboard back in it. As I say it might work better with electric because of the batteries, Mine took about a pound of lead in the nose to get it to balance, half a 1 kilo diving weight. you might need lead and the battery as far forward as you can get it.