Yes have used one several times.
Both my uncle, and a family friend have them and we have been out in them 5 or 6 times.
Several times with 3 adults, fishing in Canada. They worked well, but they are a "go slow" boat.
A 4 hp is good, we never went above 1/3 throttle,
The only scary time was when we had to go into some waves, bow is very low, wave could swamp boat if caught off guard.
Family friend used an amphibious vehicle on the overgrown and abandoned logging roads in Canada, and simply dragged the portaboat behind him on the gravel.
Crude but effective. Boat looked real bad, all beat up from the gravel and logs, BUT... it it held together and did not fail us. He beat that thing on the road for several weeks a year, for 6 years.
I would not bother with a small one.
The 12' 6", or the 14' model would be ok.