I have heard similar stories. It is intuitive that the boat needs a robust load transfer and stiffner to keep the hull from deflecting up from the tortion caused by the drive, whatever kind of propulsion that may be.
I have read of people removing the floor and having stringers glassed into the structure and tied into the existing partial ones.
I don't really know for sure, but it seems like it would make sense to do something like that, especially if there are a lot of ponies going under the engine hatch.