Nick. this will be sooo unbalanced and potentially dangerous and Insurance etc.. with that weight on a narrow beam SR will cause a lot of stress and worse as you have raised the transom height.
all you are doing is loading up both ends of the see/saw and the inevitable will happen at some point dude.
The SR'S with twins only had one baler and not two also.
engines are not over weight with the transom plate
its not the transom plate thats the issue. the greater issue in the joins either side. If Avon had designed the Rib to take that weight then there would be no issue. but they didn't Nick