LOL yeap that was a wild answer on my part, had my head up my butt figured I get a answer while I was there. With almost 700 post, ya'll need to let me have one wild answer.
Ok lets get back to why this boat has to be run with a hard right rudder. All of the answers so for play there on little part. First is torque, the prop looking from the transom to bow is turning clock wise, making a counter clock wise force on the hull. Keep in mind that this force becomes less as the boat begins its forward movement and the engine/prop reaches its top rpm's. Now add in the weight of the piston and cylinder plug and maybe the coil on the port side of the center line of the boat. Thats so for 2 down forces on the port side. Now add in the extra cavitation on the bottom side of the prop as it passes, below the transome gunnel. Now add in a little twist of the engine stand as the engine is powered up(looking at the pics, if does give any, it will give so that the prop will slightly move towards the strbd side) adding to a left turn.
If the engine must be on its side, mount it on the opposite side, cut the transom down like you plan to in the pic above, install rudders that are a little larger. Place the battery pack on the strbd, side of the radio box. Set the engine so that it will make the boat turn a little towards the right(looking down turn the engine, counter clock wise)
All in all you built a fine boat, that just needs a little tweeking