Once an aircraft is licensed as an airplane, it cannot be registered as a
glider. Some motorgliders were licensed as airplanes and the owner sadly
found out that it could not later be converted to a motorglider (at least
easily). So, the motorgliders with short and long wings would have to be
licensed as an airplane, then when the long wings were installed, it would
simply be a long winged airplane requiring a medical.

Motorgliders can often be cumbersome at airports. When you have 54 foot
wings and are landing at a 50 foot wide runway with lights on each side, and
one landing wheel allowing a wing to fall, you have an invitation for
excitement. Most motorglider damage occurs on the ground. Many taxiways
are simply built to test the frustration level of pilots. That being said,
I do not think that docking an amphib would be too much worse.

And, how do you get an amphib motorglider into a 35' boat slip? Same way
you get one into a 35' hangar - not easily.

Colin