I've a 14 ft Maravia with laced in floor & center oarframe. Lot of rocker fore and aft. Have a tube-mounted strap-on transom and 75 lb outboard 15 hp motor. The issues: heavy motor and driver sink the stern, making water flow in through laces and sinking it more...and worse when power applied. Happens also with lighter motors down to 4 hp. Also concerned about stressing seams. What is the answer? Thanks for helping.