That should work if you're carefull with the elevator. Use a little up elevator to hold the float tops parallel to the water as the speed builds up and the airplane will take off by itself.

If that doesn't work for you, start shimming the REAR strut until the airplane will run along the water with no elevator input. Then a little up elevator at the right time will take it off.

Do not shim the front strut. You already have the wing at a high angle of attack. Any higher and you risk taking off before you reach flying speed, followed by the inevitable tip stall-splash.

Jim