I'm interested to hear how you come out. I agree with the above suggestions that something is not set up right. If your floats are set up right, the plane should handle on the water darn near as good as it did on land - and with a 60, you should be getting in the air almost as fast too - maybe only 10 - 20 extra feet. Nothing like what you described. Believe me, something is wrong because it shouldn't be that squirrelly. Is your step right under or maximum of 1/2 inch behind you CG location? You said the plane felt pretty good in the air except for the extra weight, so your CG must still be fine.

Let us know how you come out. A plane that you are that comfortable with in the ground configuration should work great on H2O. The Stick is a time tested excellent design as you already know - so I'm sure you will have a great floatplane here shortly.

Jeff