Rob,
For several years and a few thousand hours, I worked a good strong 185 on PK 3500 D (I can never recall if the C's or D's are the straight floats, but these were the late model straight floats) from the Fairbanks International Float pond. Many of those launches were at MGTOW 3350, often on hot days.
The pond in FAI is narrow, so it's easy to "calibrate" where you should get airborne, by noting which airplane on the bank you launch next to.
That airplane and those floats went away, and I started operating a good strong 185 on EDO 3430's. I was delighted when they handed me the keys to that plane, cause I always thought precisely what you posted.
Reality sank in, when I realized (after a bit of getting used to the plane and floats) that I was breaking water almost exactly where I had with the PK equipped airplane, with the same loads/wind conditions, etc.
That was a wake up call for me, and I've since talked to others who've worked both extensively and they say pretty much the same thing.
This is NOT true of the early PeeKay floats, the A's and B's, and THEY are where this reputation came from. Those floats were really doggy. THey'd definitely test your skill at getting a seaplane airborne.
MTV