Hi Rolf,
You have to be careful scaling an 18ft boat down to a 14ft boat because the displacement also scales down. For example if the hull length and width and height all scale down by 14/18, then the displacement, meaning weight carrying ability, scales down by (14/18)**3. This means the weight carrying ability of the 14ft boat would be 47% as much as the 18ft boat. You might need to go on a significant weight loss program.
Good luck,
Bill