Graham, for Northcraft read BWM. Very similar boats and hulls but Northcraft never seemed to produce the volume or popularity some of the other manufacturers managed. Can't remember any real problems with them.
Adding seats shouldn't be a problem but have a think about balancing the boat if it has a large V6 engine on the back end. Might be a case of try it with lots of people first then fit seats.
Pete
__________________
|