I learned something today, relative to the original question about a PPSEL flying a Searey. If the Searey in question fits under the weight, speed, etc. limitations of a light-sport aircraft, a PPSEL can fly it as a Sport Pilot.
http://www.sportpilot.org is full of information about Sport Pilot certification. To see the "FAQs," go there and click on "Ask the Expert." One of the questions answered under "Existing Pilots" is
As an existing private pilot operating as a sport pilot, how do I add a new category and class?
In other words, how do I become Sport-pilot rated in a Searey? The answer is that you need to get instruction (both land and water) and an endorsement from a Sport Pilot CFI or better, and then get a proficiency check from a different Sport Pilot (or better) CFI, fill out an FAA form, and get an endorsement from the instructor who gave you the proficiency check.
Then, still being PPSEL, you can fly the Searey on land
and water, with a passenger if you want, as long as you obey the Sport Pilot restrictions listed here:
http://www.sportpilot.org/learn/final_r ... opsis.html. Basically, the only things you can do as PPSEL but not as Sport Pilot are flights to further a business, and night flight.
The Sport Pilot regs are in Part 61 Subpart J, beginning at 61.301. The EAA has done a lot of work clarifying questions that aren't directly answered by the FAR text, such as this one, so the sportpilot.org site is really a more informantive source for this.
Best Regards,[/i]