Cool idea, but a corvette could usually ram a U-boat and get away with it, the original design was based on a whale catcher and had ice strengthened bows. I built 3 of these kits in the past, one Bluebell, one converted to HMS Primula (short f'c'sle), the last converted like this
There is a standard corvette hull under the extra plasticard but far fewer common parts than I would have liked.
Scratch building is addictive, I think it is time for me to start again