You are right,on amphibious floats with full fuel you you are limited in passenger size. But considering the range of the CT I never had problem with half fuel and a passenger.Not sure about your question on landing in the grass on straight floats. At the airport where I am,after summer, float planes land on the grass and are stored for the winter. They take of on a trailer pulled by a pick up. As for my amphibious floats, when the Ukraine specialist sent by flight design had installed them, he would go with the plane in very rug grass surfaces without problem. I however avoided to do it myself. I have the installation drawings and the flying manual for the floats should you be interested