Not me Wyvern as you know, but the subject came up at a meeting a couple of days ago, and it seems that there is still some residual experience out there.
Dick Stratton, CTO at the British Gliding Association was in a previous life on Sunderlands and then had a hand in testing the Saunders Roe Princess. Also, Darrol Stinton has done some floatplane testing.
If you haven't got their contact details, drop me a mail privately, and I'll let you have them.
Also, the old BCAR Section D has some handling advice on seaplanes that's worth reading.
G