Some of the Coot's key attributes/compromises and why it's still okay to build one

It has 7-degrees of dihedral

• Which allows it have lateral floatation integrated with the wing structure and also have the flying surfaces out of the water so that it can... you know... take off
• Lateral buoyancy close to the longitudinal axis allows it to step taxi with greater inherent stability than a floatplane or a hull-type seaplane that incorporates outboard sponsons
• Integrated sponsons simplify airframe construction
• This dihedral also makes it heavy in roll
  • It will never be a personal fighter aircraft

It has an integrated buoyancy hull/fuselage (it's a flying boat)

• It should be more boat-like in water handling
• But it has to have a pylon-mounted engine
• And it has to have comparatively high thrust-line
• Lake hasn't worked this one out either - because it's an attribute and not a problem

The fuselage has to balance aerodynamics with hydrodynamics. 

• It must:
  • Enclose the occupants
  • Support the structure
  • Fair in and contain its retractable landing gear
  • Keep out both wind and water (i.e., both fly and float)
• Thus, it must also:
  • Taper rapidly from the cabin enclosure, wing spar carry-through, and engine pylon bearing structure to the tail
  • Have a hard time maintaining unseparated airflow:
    • Through the prop disk
    • Over the rapidly tapering tail
      • So, it may also end up with some yaw instability - Something Cessna, and most floatplanes have a hard time with too; although the cause for them has more to do with the floats blanking the tail while in landing configuration

So, its hull has to eventually end somewhere in order for it to streamline

• This ends up meaning that
  • Its wings can lift more than its hull can step
  • It can fly off of land heavier than it can lift off of water
  • It is likely that every amphibian in existence has these same attributes

It is constructed primarily of wood, steel, and sheet aluminum

• That rots, rusts, and corrodes, respectively
  • Duh!  No revelation here
• It requires traditional building techniques
• Readily available non-exotic material

Plans-built means that the project can be scaled to suit the builders budget and space constraints

• Builder has to find, scrounge, evaluate, and  select everything
  • Couldn't get much better than that!