Frank,
Years ago I built a bbsb that had a lot of rocker in it therfore a displacement hull. Loaded down with a dog, anchors, decoys, gear and myself, powered by I 15 horse the boat would move a long at about 10 mph. The boat was not fast but, I felt safe to take that boat out in the worst possible weather.
Two years ago I bought a used classis bbsb made of 100% fiberglass also a displacement hull. The boat Loaded down with same load as mentioned above and powered by the same motor The boat would run at about 14 mph.
Just this pass summer I puchased a planning hull chadwick box from a buddy of mine. Wth the same 15 the boat moves out at about 20mph...nice smooth ride...love it!. Quite frankly unless I have a place were I'm going to be rowing the sneakbox then I propbably will stay with a planning hull from here on out. Good luck...
I hope this helps ask if you have more questions.
Zane