I havn't driven a car with floating hats, but our Targa car dosn't have them (does have knock-off valves though). And I don't have them on my car eather (got 355mm dba 5000, with porsche 6 pot monoblock). Now i've got a big master cylinder in my car i barly have any knock off. And the Targa only gets knock off in long, down hill stages.
A guy with a 997 turbo goes to our track days, and he just put brembo floating hats on, and he said the only diference he noticed was they were noisy. But that's only at super sprints, are you planning to do more than super sprints?